[Cainehill]

Nothing would keep you from breaking an alliance - you'd simply get a warning that you'd be breaking the alliance, and the other player (and possibly _all_ players in the game) would get a notification that a treaty/alliance has been broken by so-and-so.

And again : the even more important aspect is that when someone goes AI, the AI could know about treaties, alliances, as opposed to completely trashing a MP gamer as often happens now.

( And yes - I would say it ruins a game at least for the person who had a treaty, their armies on the other side of their empire, and gets rolled over when the other player goes AI. )