Akismet have updated the procedure to recover a lost API key.
You can enter your email address and Akismet will send your account API key. Go to: http://akismet.com/resend/
Akismet is a hosted web service that saves you time by automatically detecting comment and trackback spam. Each time a new comment, trackback, or pingback is added to your site it’s submitted to the Akismet web service which runs hundreds of tests on the comment and returns a thumbs up or thumbs down. There are free and paid for versions.
