Alpha Centauri is much more conducive to abject paranoia than Diplomacy, though -- at least, the way we played it. We would start a game by taking turns on the same machine, for the first 10 turns or so, during lunch. Then, we would go back to work, and take our turn on that machine when it came up (we'd VNC into it). This way, the game doesn't disturb our actual work too much, and each player can take as long to micromanage his cities as he wants.

Thus, all the player-to-player interaction takes place on back channels -- through email, or clandestine meetings. This fact, combined with the knowledge that one tech advance, or one airstrike at the right time, could shift the entire balance of power, results in truly Cold War-grade levels of paranoia. It is an exhilarating experience, in a way.

I should probably mention that no relationships were ruined by our games, either, as far as I can tell. A game is still only a game, after all.