Jim
I think if you can easily take South America or Australia in the first couple of rounds then it is worthwhile as the extra 8 or so bonus can make quite a difference around about the first cash, though after that it becomes virtually worthless.The big mistake is using a cash to take a continent as it both ties up your own troops and more importantly often cripples another player leaving him vulnerable to another player.
As for the idjut comment I find that they rarely win,unless getting spectacular dice,if the rest of the field are experienced players. What they do tend to do is 'hang' somebody and consequently hand the game to somebody else,this of course evens out as you are as likely to be gifted as robbed but it does spoil games. The very best players tend to make a killing move in such a way that the consequencies of failure are not neccesarilly terminal,the idjuts dont seem to give a damn and often cripple somebody to the point of no recovery with often highly speculative attacks. My answer is to simply not invite the idjuts to my games and to avoid joining games where they are likely to show up,mind you we all play like idjuts sometimes
