Can they really? Spam detection isn't mathematical science, there is no guarantee that the solution to a problem is always going to be the same. Spammers aren't forced to identify themselves, and they are growing half enough of a brain to imitate what they believe should look like a human response.

I would honestly be a lot busier without it then with. I have never run anything remotely in the realm of popular or high traffic, and I've been nailed with so much spam that not having Akismet would have probably driven me to the brink of detonating some semtex in my datacenter.