[reuben_tate]

I think it should be allowed, but only under the host's discretion. For example, if signups for one are at the same time as when another game is about to end, then there isn't much of an issue.

I think the host should ask themselves/whoever the following questions if someone wants to join their game while already playing in another game(s):
-Would the host(s) of the other games be ok with it?
-Does this person have a recent track record of being reliable enough to be sufficiently active in both games?
-Is there a high possibility of confusion akin to what psychoangel said? (Confusion on roles and who's who).
-Are signups slow and is this person a new player? If not, perhaps giving others a chance to play would be better.