I've split this post into it's own thread so it can be discussed in context.
"Guests" are not members. All a guest can see is topic headings and not the actual posts within the threads. We don't know who the guests are. The will most likely be spambots. However, the thread titles are searchable within google. We made this change in 2010 at attract members.
I'd have to look into the logs to find out the exact figures, but a quick look at the "awaiting activation" list was 6 valid accounts in 54 new accounts. That means there were 54 NEW accounts, but only 6 had valid email addresses. We used to delete these accounts as they appeared, but it is too time consuming to do all the time. We tend to delete the account if they manage to get past activation and then post.
Of the 1900 accounts, I'd say 10% would be active participants. Last time we "culled" the site, we caused "problems" with members that only wanted to lurk and not participate.