Akismet learns, Captcha doesn't

I just had an interesting spam attack on my site. It was identical spam contents posted to a bunch of my comment forms. I am using CFFormProtect (of course, I built it ;). The first couple of attempts got by Akismet, but my other spam detection methods still prevented the spams from posting (yay!). But what happened next shows where Akismet shines and proves that these methods are way better than Captcha. After Akismet had a chance to analayze a few of these spam posts, it started marking them as spam. The contents were exactly the same for every post, and Akismet was able to dynamically learn. However, when a spammer breaks past the Captcha on your site, he has a free pass to all of your forms.