One of the best things about Planetarion is that it encourages team playing - all the people in your galaxy have to work together if they want to get anywhere in the game.
It requires communication and an understanding of tactics. The 1337-types who claim to have huge fleets or lots of 'alliance buddies' don't get very far, because they can't bluff when there's ten thousand ships attacking.
There's an IRC server, including a web interface, which, although an out-of-game communication tool, is essential to maintaining a good galaxy.
Planetarion (or 'PA') is a pretty nifty game, overall.