I just found something very strange.

One of the forums I administrate has a new user and a new post, saying:
Give me link to SEO software (promotion, advertisement, etc.). I'm need it to promote my new e-shop.
Thanks.
Now, normally it goes the other way around. A new user appears and posts, telling me how to find SEO software (or eastern European flowers, or naked celebrities), or just sits around without posting in order to try and get more links to the web address in their forum profile. The former gets their post deleted as soon as I see it, followed by their account, and potentially an IP ban. The latter gets deleted eventually, but since I tinkered with the board to hide post-less users from all the lists, leaving them there doesn't help them and doesn't hurt my users.

It's all a bit weird. Personally I have a policy against deleting accounts that haven't done anything obviously wrong, but there's definitely something fishy (hence the lack of links in this post).