The Register has a great interview with a link spammer:
“You could be aiming at 20,000 or 100,000 blogs. Any sensible spammer will be looking to spam not for quality [of site] but quantity of links.” When a new blog format appears, it can take less than ten minutes to work out how to comment spam it. Write a couple of hundred lines of terminal script, and the spam can begin. But you can’t just set your PC to start doing that. It’ll get spotted by your ISP, and shut down; or the IP address of your machine will be blocked forver by the targeted blogs.
This is pretty much a must read. Hat tip to Jeff Quinton.