I wish Akismet was available for forums too, it is superb, catches 99,9% of spam comments to my blogs.
And for a real satisfaction then I ban those spammers with one click, so they cannot even see my site any more. :kissass:
I know it can be dangerous if the spammers use proxy servers to hide behind and dynamic IPs, and later a normal user would come to the site from that IP, but oh well… You cannot get everything.