Facebook charity: don't ask, don't tell, don't join?

Crunchgear raises an intriguing question about online charity and privacy:

In discussing several things with my brother this Thanksgiving weekend . . . he brought up something Facebook-releated. See, he doesn’t join groups promoting a cause (”FreeRice,” for example) because he doesn’t want to be seen leaving the group later on, privacy settings@ notwithstanding.

What, you don’t support feeding starving people anymore, you jerk?

@It’s a social phenomenon. How do you show your support for a cause on Facebook without later being seen retracting your support? @It’s something I think needs addressing, along with the pocket veto, a term I coined some time ago describing friend/group/whatever rejection without rejection.