lidhaegn.. Italy/Russia is a very common and fantastic alliance. They share many common enemies and don't have as many trust issues because they aren't physically adjacent for a while.
I've probably said this 50 times in the past, but it seems someone always wants a definition for metagaming.
A player is seen to be metagaming when they take influences from outside the individual game (including other games) into the individual game. This is a fairly vague definition, so I'll include examples below. It's debatable whether or not metagaming should be prohibited, but I am personally against it, and I've explained many times.
Of course it's impossible to completely eliminate metagaming as lidhaegn explained, but that does not make the pursuit of it's minimization any less worthwhile.
Example A: Two players are husband and wife. In every game they join they immediately and unconditionally ally, because they would rather not damage their marital relationship. This is metagaming, and it puts the rest of the players in the game at a severe disadvantage because they do not share this same relationship.
Example B: Two players work out a deal in which they help each other win in two separate games. This is metagaming, and has the same effect as the previous example.
Example C: Two players find that they work very well together having just peacefully resolved a game in a two way draw between them. The next game they encounter each other, they immediately co-operate. This is metagaming and has the same effects as the former two scenarios.
It's apparent that Example C seems much less 'illegal' and it's extremely hard for a person to ignore their past experiences, for how else would they learn and improve their diplomatic game? It is true that Example C is potentially less damaging, because in this newest game, the other players may share similar relationships, so there may or may not be an inherent disadvantage.
However, this is not always the case. While metagaming is more acceptable in face to face games where it's typically a group of friends who all know each other and share the same relationships, it can add an unfair element to online play here. This is because other players in the game do not share the same relationship as the metagamers and have not necessarily been given the same opportunity to establish a similar relationship. Instead, they are put at a disadvantage from the start of the game, and the metagaming cartel may be unbreakable and unbeatable, especially to unsuspecting players.
There are several solutions to this that do not involve publications of personal information, or blacklisting and alienation. Most involve awareness and a willingness to minimize one's own metagaming.
Firstly, avoiding all cases similar to Examples A and B. There is absolutely no excuse for these forms of metagaming. If you know someone else on this site in real life, be prepared to play with them in a similar fashion as you would with any other stranger on the site. That means stabbing them, coercing against them, or whatever it may be.
Secondly, to avoid Example C... you could make an effort to memorize other players purely by country names. This is what I do, and it works quite well. I hardly remember the usernames of people I've played in the past. Alternatively, if you adopt a rigorous play to win style then you'll recognize that alliances are due more to circumstance and necessity rather than how well you got along with them in the past. Be prepared to stab and be stabbed by your most loyal past allies.
As well, if anyone's willing to implement the option... anonymous games would also almost completely eliminate metagaming. However, as Kestas has finished most of his development, it would have to come from another php developer.