I PMed GIK about that very issue. If the site starts doing anything other than donations (ie banner ads, subscriptions, sponsorships, etc), there are certainly some issues that would need to be addressed ahead of time. I don't really have the answers to those questions (ie, should the site incorporate? if so, then how? Would an LLC work? what about non-profit status, etc?)
My guess (and this is just a guess) is that as long as the site stays funded by donations only, we probably don't have to sweat things too much.
The main thing is that those issues need to be addressed before any big changes are made in paying the bills for the site. The last thing any of us wants is for someone to run afoul of the law...or even worse.. the IRS...