I delete a few people every day who either spam links (usually pharmacuticals) or add their own, unrelated, spammy website as their URL without ever posting. I have email verification turned on but they seem to be automated, which means they have a bot to verify their account via email.
This brings up an interesting idea.... would forum owners be interested in a TRADE -- you allow me to post HIGH QUALITY CONTENT on your site in exchange for relevant links in my posts? Email me at info AT webmasterlabor DOT com with subject line of CONTENT for LINK forum BARTER