Pretty much anybody with a bb style forum gets oodles of these guys. The clutter they cause tends to bog down the mysql database back end, causing the site to be slow, unresponsive an occasionally crash...like these forums are prone to do (as well as many others). Most of them are bots.
Two levels of enforcement that tend to work are:
1) Increasing the obfuscation on the secret word for account creation to maximum. (For some reason the good bots can still manipulate the first two levels of obfuscation.)
2) Enforcing hand-approved account creation. (This one is a pain for a large site, as the approvals required can quickly out-pace and administrator.)
