I think if you want to make sure its well back/insured you should give 50% or even 100% of any coins deposited into escrow in the case of a default. By this I mean if 50 users deposit a total of 100coins then you should give escrow 100coins in the case of a defunct.Also I would make sure that the escrows are split up between escrows. Maybe a max of X coins per person.
You could also do something with multikeys and have a privite key generated and signed with multiple keys give to X trusted members on the forum. You keep the names privite and in the case of a defunct that one would start a thread and the other would reveal themselves.
That would limit my trading possibilities, and would overall make me lose a lot of money (if I hadn't sold most of my BTC above $200 to buy back cheaper, for example). I think shares and things that I hold over a long period of time would work better
Update, started getting my interest payments into my account, will wait a few days to test the withdrawal and all that, but so far so good!
There won't be any problems with withdraw, hot pocket has a lot more coins because of loans I issued with my own capital previously