Some wordpress bloggers like akismet. It does do away with a lot of spam, but it is extremely sensitive. It likes to block a lot of legit stuff too. If I remember right you can sort of teach it to learn, what the success rate of this is though I don't know. There are several others out there that are not as sensitive and do a good job with spam. A lot of them are buggy though.

I wouldn't mind seeing something like this though in the future. It might even be nice to see it happen or tested here see more at unity. How many times are things posted here that are obvious spam and they sit up here for an extended amount of time before someone finally removes it.