[rdonj]

This is actually the most complicated question to answer of the ones you've posted so far. First, it depends on the kind of game that you've joined. Often in the first post of a game thread, the game host will state outright whether diplomacy should be machiavellian (nothing you say to another player matters, and you don't have to respect any agreements/whatever that you make with them), or that diplomacy is binding. In a diplo is binding game, breaking agreements with other players is frowned upon and could hurt your reputation. Many of the more experienced players are quite trustworthy in such games, but there are also those who feel that if it is to their advantage to break a deal with another player, that it is their right to do so.

There is no active tracking of people who break agreements... only your own memory, and the memories of those who hear about such things. So if you want to find out whether someone is trustworthy you have to play a game with them, look up other games they've been in, or ask around and see what other people have to say about them.

For the record, in my personal experience most people do not break treaties in the diplo is binding sort of games. If you are worried about playing with trustworthy players, joining only those sorts of games is probably sufficient to avoid being backstabbed.