Hi Sarah!
I am a member of bookcrossing.com (see my sig line) and have released a couple of books into the wild, but they were never journaled as being found. Also, I've passed books on to some of my friends with the bookcrossing numbers inside the front cover but they have never journaled an entry. I think it is a wonderful thing (the read and release concept), but I guess there is not much interest in my area.
My sister-in-law is a librarian and she is also a bookcrosser. She got me started, I guess. She has more trouble than I do with releases because she lives in a very small town.
I am not really up on all the terminology so thanks for your definition of a bookray and a bookring.