I think I'd also like to propose the term "anxiety of audience" to describe the strange self-consciousness that grips one when one's friends/followers/network on a social networking site change in unexpected ways. See, over on twitter, ever since I joined the "Technical Communications" twitter group just to see what it was about*, I've gained a couple of followers whom I don't know. All I can determine from their profiles is that they're tech writers and that they live overseas.
So, I see this, and I think, "Gosh, I should twitter some stuff about tech writing, because that must be what those people are interested in, as opposed to my usual natterings about science fiction and BBC radio and tea." There are two problems with this argument: First, I'm not sure that I have any profound thoughts about tech writing that can fit in 140 characters or less. Second, there's a fair probability it's actually my natterings about science fiction and BBC radio and tea that interest these folks, and the fact that we share a profession is much less important.
*Right now it seems mostly to be about people twittering that they've joined the group. Hmmm.