MadMonkey: Not a bug, but I think is a good feature. Sometimes a team just needs 1 or 2 more people, and for players who like to play - being able to sign up for that team to play, then possible go back to their original team is a nice feature.

I think there was once a bug where the same player was playing in the same team challenge/match (against themselves) - I'm not sure if that was ever fixed or what came of it.

But as long as that does not happen - it's nice to be able to move teams. (But I would support maybe some kind of limit - like you can't join anouther team for 30 days since you joined another or something)