the known user list shows loads of spammers => http://screencast.com/t/GvoDzikyGdu
in the configuration of your plugin:
Ignore Spammers Yes
Do not track visits from users identified as spammers by a third-party tool (i.e. Akismet)
I selected to ignore spammers but it seems not to be working. I admit, some of the SPAM got through and I guess your plugin doesn't delete a user from its known users DB if his comment was marked as SPAM later on?