Of course deleting idle & old fellowships can be nice - sometimes it is nice to keep just to see what was there and such.

What I would like to see is if a fellowship has a pawn BIG BOSS, then just "hide" it in the fellowship list.... and include a "show all including hidden fellowship" links to view the old ones.

Since you also have to be careful to make sure all tournament games are complete in a fellowship - and now you also run into a problem if there are current stair games, etc.... So hiding them would be the best option in my opinion.