I've recently been looking into the spam that hits drupal.org and yesterday I've finally found out why they do that and that it actually works. Until I block the accounts at least.
A blocked a account will give any visitor a "403 access denied" message. Drupal logs these incidents. It also logs the referer of these requests, so I am able to see which page the visitor was looking at when he clicked on the link to the blocked account. Most of these pages are search resulte of google and other search engines. And of course the visitor was looking for porn of all different flavours.
