I usually do not chime in on online forums, but this issue has bothered me since I began to play in conquer club.
This diatribe obviously excludes team games, because teams games are forced alliances--it is always good to have your teammate alive to help you out in defeating your common enemies, as BOTH or ALL THREE of you will get points if any one of you is the "last person standing".
Generally, alliances are a HORRIBLE idea in conquer club (ESPECIALLY unlimited cards games) for 2 simple reasons--1)there are no second place points in risk, and 2)both parties to an alliance have a compelling interest in breaking a treaty to win. An alliance is counter-productive and pointless because you are only strengthening an opponent you will have to defeat in the future, in order to get the points.
In an unlimited cards game (in any map, and regardless of if the game is unlimited or 1 fortification), holding a continent is the main reason that people make alliances--but is this worth the cost of an alliance? I think not, because after the cash point reaches about 20, it is impossible to station enough armies on your borders to assume that someone will not be able to break into your continent Plus, holding a continent will generally not give you enough armies to eliminate a player and take his/her cards before he/she cashes in order to stay alive, anyway. So this is not a good reason to make an alliance, plus you still have the downside/risk the other player breaking the alliance or getting eliminated and not being able to help you out AT ALL.
The other reason people make treaties is to break a very strong player. Except in flat rate game, this is a HORRIBLE reason to make a treaty. Why? Because even if someone holds a continent through several turns, the big cash point (20+) will eliminate any advantage they had in turns 1-6. Hypothetically, assume that in a 6 player game, one player gets all his armies in Europe and is able to take Europe within 2 turns. [This is about as likely as being bitten on dry land by a shark, being struck by lightning 7 times, or winning power ball twice in a lifetime--all these things have happened, but I wouldn’t “bet the farm” on a player getting all his armies in 1 continent.] From that point on he will be getting between 8-10 armies a turn. Although it seems like a lot, it is impossible to knock others out with 10 armies this early in the game, because the randomness of the placing of the other armies would not allow him to travel over other players to knock someone out (and he would only get 2-3 cards if he could accomplish this feat--good, but not always worth spreading yourself out to the absolute maximum!). Then in turn 6 someone will cash in for 10-15 armies, knock him/her out of Europe, and everyone is back to where they started, except now the player who had Europe will be very vulnerable to being knocked out because all his armies are in one place.
This situation is when weaker players will try to make alliances to break the strong player, but what is the difference (to the weaker player) between being knocked out of the game in turn 3 versus turn 6? A player who is on the verge of extinction at this point will benefit short term from the alliance (not being killed by the strongest player), but in this case, what is the difference between being knocked out in the 3rd or 4th round by the strong player as opposed to being helped by an alliance, only to be knocked out by the player you helped in the 3rd & 4th rounds? You still get 0 points for all that work!!!
Another argument against alliances is that analyzing an alliance from both sides (a player who is planning to break the treaty, and a player who made the treaty in good faith and is planning to keep it for the specified number of turns) neither is better off using the principles of Game Theory/Prisoners dilemma. Basically, game theory says that people act strategically to maximize their desired outcomes. But in conquer club only 1 person can win (the desired outcome), so the best case scenario is that you increase your chances from 1 in 6 to 1 in 2 through an alliance. However, whichever player in the alliance gets strongest first will probably break the treaty because the outcome desired (being #1) would be better served by breaking a treaty while the other party least expects it--Why? Because the weaker player will have cards, will not be expecting the attack, and (once again) the only positive outcome is 1st place. This scenario is just too temping when one player is a lot stronger than the other. Generally, this is why in the prisoners dilemma, BOTH suspects will rat each other out--each one hopes that placing all the blame in the other suspect will allow him to go free. The risk of being a rat is slightly less than confessing, because prisoner #1 cannot be sure that prisoner #2 will not be a rat, the risk of being a alliance breaker is less than being a good alliance keeper, because risk player #1 can never be sure that risk player #2 will not break the treaty.
There are only 2 possible outcomes from an alliance. 1)Both parties keep the treaty perfectly and end up being the two strongest players in the game. However, at this point the game just comes down to chance--who gets the better dice rolls/card--so this situation is no better than just playing a straight game with no alliances--all that matters is luck in the end, anyway. 2)One party breaks the alliance and eliminates the other. However, since you can't be sure that the other person will not break the treaty, this really doesn't help that much, either--unless you REALLY think you have a sucker on your hands.
All the above being said, I think there are 2 exceptions to this rule.
1)Flat Rate/No card games
In these cases, holding continents is the most important factor that determines victory. If one player gets a continent too soon in the game no other players will be able to knock him out of the continent because the max card cash-in is 10 armies. All it takes is one player holding a continent for about 3 turns for him/her to be able to put 10 armies on a border and ensure his/her victory very early in the game, as no one can break the continent and the constant flow of armies from it.
2)Alliances work when you are playing with a sucker who you can give an alliance to and then immediately break with him--provided that you can eliminate him in the following turn. I find that this strategy makes people VERY angry, so you MUST be able to eliminate that person within 1-2 (MAYBE 3--although you are taking your own life into your hands, here) turns. Some people REALLY get off on retaliation

(like being "on tilt" in poker--emotional decisions in risk are generally bad decisions).
I used to feel bad about this strategy until I encountered my 10th or 11th person who asked for an alliance before the 5th turn in an unlimited cards game (there is a name for these kinds of people--TOOLS)!! Anyone that stupid should really be eliminated anyway (Social Darwinism at its best--they are just too stupid to live!)
Finally, the objection that negotiation/collaboration is just part of life and part of all risk games is fallacious. Why? Because there are few, if any, perfectly zero sum situations in life (the only situation I can think of is a cage fight to the death--not too common these days). When a player is confronted with zero-sum situations like in risk, they should only be interested in first--nothing else matters (its like what Arnold said in Conan the Barbarian--“What is best in life? To crush your enemies, to see them driven before you, and to hear the lamentation of their women” ).
To me, Risk is the perfect game because power is always in the balance as the board was set up to cause tension between players. The whole point of the game is to put people in a zero sum situation where they will be forced to do something few people do in real life--wage all-out total war against others. There are no other considerations in risk, so why mess up the perfect balance of the game as it was set up? If you want to collaborate in an activity, you should try quilting or join a book club or something--risk is not for the weak or the co-dependent. Having an alliance in risk, is similar to taking “loans” out of the bank in Monopoly--it completely defeats the purpose of the scenario the game was meant to simulate.
Side note--if you want games that include some collaboration/negotiation (I know of no online games that include collaboration/negotiation, to a great extent) go to
http://www.boardgamegeek.com they have some pretty good games that have interesting aspects of this sort. I don’t work for this site or anything, they just have cool stuff.
This is probably the longest post in conquer club history, but it annoys me to no end that I win some games simply because people make stupid alliances--I like the challenge of winning games based on strategy--not other players poorly thought out alliance/collaboration strategies.