It's alright, Artful - your name's on the guest list! Don't forget that most of even the chattiest posters don't actually know each other personally, so it can't be that cliquey. I did feel much the same as you at first, but I just took the plunge, joined in some threads, and was delighted to find no-one said "who asked you?" or anything similar :-) Glad your mind's been put at rest!
BTW, CORBYLOON - this is my 499th answer. I'm getting dead excited now. What kind of chocolate cake is it exactly? I hope it doesn't go all squishy in the post. Mmmm. littleoldme like chocky cake. Num num num.