If you're a member, you can sign guests into the club.
If you're a guest, you can't sign a member or other guests in, unless you're a member of a "Guests only" club, of course, in which case you arre in fact a member...
Wait, what was the question again?

Seamus

OK, now I remember...if you're a member, you can PM bona fide big stars like me and Clinton Hammond and Kendall and Alaska Mike and Jed Marum who wouldn't normally give you the time of day if you greeted us on the street or e-mailed us, or even phoned us.
But we (don't we guys?) take our Mudcat superstardom very seriously.