I donít think that posting this as a status on FB means suddenly that anyone who wants to go can, unless the status specifically says so. I think the guy was rude to presume he could just come along all because he saw it as a status.
However, what about if someone posts this in a FB event? Whenever someone creates or RSVPís to a FB event, then itís published to their wall. So if my friend Mary RSVPís to an event, I see it as it has shown up on her wall, and I decide I want to go as well, can I just do that, too? Of course I think that depends on what kind of event it is. For instance, if itís something public, like a play, I think itís okay for me to RSVP that Iím attending because itís a public event. If itís a private gathering, not so sure. In one way itís being made public because itís an event thatís showing up everywhere, however, on the other hand, itís something of a more personal nature, like a birthday party for someone or similar.