With a dated version of vBulletin and no captcha, the SDMB is quite vulnerable to spambots.
From time to time, I’ll see a username that looks fishy. Google it, and it will appear as a new user on hundreds of message boards; a sure sign of a spambot. Sometimes, the username is obvious, for instance I just saw:
Anyone else here Google the names of new users for shits and giggles?
I don’t, but as a tangent, what are those wavy text boxes thingies meant to defeat bots called? Does that SDMB use them?
Captchas. And as the OP mentioned, no we don’t.
Not exactly, but I did report our newst member “clickforfreestuff” a few months ago.
Banned before he/she/it made a post 
Thank Og. It usually takes me two or three tries to figure out the letters they’re expecting.
Captcha? Since I didn’t know the term, I didn’t recognize it in the OP.
I swear I’ve heard some other term to describe them.
I promise, they’re called captchas.
Risha- Me too. I hate the damned things and I’ve given up on some things after three or four tries.
…Wow, sometimes a user name is just mildly witty and now (or not) very well thought out… 
ThisSpaceForRent
The only thing I get is my definition =)
Oooo baby, google me some more! lol
I do it for a more useful purpose. To see if the new registrant needs banning. And I know at least three other mods do it on a regular basis.
The best news for the board is the relative lack of sophisticated bots. I’d estimate only 1/50 get through the registration process and post. Probably even fewer than that, now that I think about it.