Suggestion Box

I do not like having e-mails sent to me which try to involve me in "pass it on"-type groups and such--I received two of them today--and I don't care for campfire invites either. I realize it's simple enough to turn them down, but it's a bit of an annoyance to see you have mail and then to find these, which are often from people the invitee has no current communication with. (That is, they're similar to Spam.)

Perhaps there can be some kind of system whereby a user can "block" such things--or better yet, announce publicly that they are not interested in being involved? For the latter I'm thinking maybe something like the IM list which shows a little link if the user is accepting IM's or not. Maybe something similar, which says if the user is accepting invites and/or pass-it-on involvement or not? At the moment I've had to state this in my bio block, which I'm sure is likely to be missed by most people.