In this case, iRidePigs mentioned that he is introducing some players to the game, so a reasonable player can assume that the game was:
1) Originally created with the intention of keeping the password private
2) Contains two or more people who know each other
3) Is a teaching game, so players can expect a somewhat low level of play
However, assuming that ALL password protected games contain players who know each other is incorrect. For example, see "every game in the gunboat tournament, ODC tournament, the Leagues, Masters, etc."
Also, despite our best efforts on the mod side, it is also technically incorrect to assume that all NON-passworded games DO NOT contain players who know each other in real life. Public games can always contain cheaters. Public games can also contain real life friends at any given time. However, since metagaming only becomes metagaming if that friendship is used as a pretense for an alliance or in-game action, plenty of public games can, again, technically contain real life friends. Admittedly, this is a grey area, but mods can pretty easily spot metagaming in all its forms.