The strategy that the original poster is referring to is the fort strategy. Basically what you want to do is keep building armies on each of your territories. This way, if someone decides to break you, you can regain your land back no problem.
Also, while you build up you seem like you have no real force. eg. I own SA and i have 15 guys on each country, whereas the guy who owns africa has 35 guys on North africa and 1's on the other territories. 35 can beat the 15 on brazil sure. but all in all i have more armies than he does (15x4 = 60, 25 more guys!) and if he wastes time taking brazil out then i will just get it back

With only 15 guys on brazil i offer no particular threat to the person holding africa (even tehn if you play with noobs they will break you for no rhyme or reason, so you just need to play carefully) and can usually chill for a good part of the game and stack up.
Anyhow, this strategy works good in flat rate because with all the other guys involved in an armament buildup along their borders, one of them will crack and destroy a percieved threat and then you can come in and sweep it up
Note that this is a VERY poor strategy for escalating games. It only ensures that you get eliminated last. :p However, it may work if you get lucky and the games are unlimited forts.
Stormur has posted another version of the same strategy that is essentially aimed an having a percieved non-aggressive aggressive stance by having a huge attack force behind the border that will dissuade people from breaking your continent; eg. if i own SA i will have 5 guys on brazil and venezuela and 50 guys on peru - if someone is dumb enough to break me, I can unleash the 50 guys on them - In an even game they would have to split their 60 guys all across their borders (minimum 3 for africa and NA) and wont be able to deal with 50 guys, so they won't try and break you.
I dont think that this is very successful in esc. games either (perhaps for the first few rounds). I guess you can try it out and post results.
best of luck!
People teach their dogs to sit, it's a trick. I've been sitting my whole life, and a dog has never looked at me as though he thought I was tricky.