Re: Akismet doesn't catch spam
Akismet looks at a number of factors – ranging from email addresses to IPs and the texts of posts.
_ck_ also suggested not trying to test Akismet with spammy comments:
I don’t recommend trying to purposely cause spam to test it because akismet might flag you globally as a spammer and you’ll end up being bozo’ed across multiple forums/blogs.
I’ve marked a few posts as spam on my forum, and noticed that every subsequent comment by that user got flagged by Akismet. Your mileage may vary… but you’re welcome to take your chances.