If it's a non anonymous game, then it's definitely cheating-especially if the other players don't know til too late.

If you see a friend playing a game, simply either not join, or if you do, send a global message so everyone at least knows....

why is it definitely cheating in non-anon? Seems like it would be cheating only in anon games.

in anon games you don't know who is who, so theoretically you can't find your friend.

Right that is why it is definitely cheating in anon games because you have violated the anon part. But what are you really violating in the non-anon games?
nm I guess my round about point is I don't see why people play non-anon games. Seems impossible for there not to be metagame influences on them.

if its NOT an anonymous games, you can clearly see who is who, so joining one with a friend and allying (as you said as the case) is cheating.

If u see ur friend in the game, don't join unless you at least let others know so they can decide if they want to play.
Best way- either play with all friends or none

Allying with a friend is not cheating...
Going for a game with the decision of allying with a freind no matter what country both get or what happens is cheating...
It's difficult to prove if it was defined pre-game or ingame...

As others said, the easiest way to prevent it is not playing with friends, but it is not forbidden.

I don't know, I've played with friends before, and I ally with them or stab them all the same as I do anyone else... I don't have seven friends on this site to play with, so I can't just play with all friends. I do see how announcing it to the group you're playing with is a good idea, but that would make them more inclined to ally against you, would it not? Well, in some cases...

well then what's the point of the diplomacy aspect if you can't have an alliance?

You can have an alliance...

You can't have a pre-game alliance...

Friends or not friends it always depend on the way you play the game.
If you play to your best and eventually ally with your friend if this fit your interest, no problem. But if you start the game with this alliance prearranged and nothing that happens will change that, then it´s cheating.
And like someone said, is always better to tell the other players about that before the game start, so they can choose if they want to play or not with people that know each other out of the game.

@rdrivera2005
In our "only speak Portuguese" game, did you notice that Master_Chavix was my friend?
I don't remember if I told the players about it or not.
:D

I don´t remember too if you told or not, but I didn´t notice inside the game.
And in the same game I (or Jesus) told everybody that we are friends that work at the same office and everybody agree to play with us (and we ally and stab eachother at least two or three times during the game eheheh).
And the game was a great one (at least to me, that got a draw after been down to 3 SCs for years :-).