It could be some kind of automated joining script, they sometimes use message boards in this way just to get a website link (usually porn or pills) in the member list. I don't think you get to add a website till after you joined here so that doesn't work, but a bot wouldn't know that. Anyway it might just be ordinary people, some of them will be for sure so I can't just delete them. If it gets out of hand we'll have to add a human interaction question in the sign up.
The automated thing sounds likely. I'd guessed it was just some person arsing around, but there's the occasional non-posting member with the same random-word-plus-two-numbers type name going back a few months, so it looks like it probably is automated. And when one or two appear or disappear under Online Now, it seems to be at the same time. I just thought I'd mention it. I mean, it could have been aliens. I guess the bots just got a little carried away today.
Yep, I'll vote for the bot too (although there may be one or two real users in there) they all have numbers at the end, which is a dead giveaway...