Good grief. If one person goes to all that trouble, that person is a mental mess and truly needs immediate help!
Onyx, in some cases, it might be a lone nut type of individual, particularly the types who do it on sports forums and such. (I first learned about this phenomenon on a NASCAR forum.) But increasingly, fringe political groups are using it as a tool to try to drive political debate on active websites such as this. Probably happens over on DU and elsewhere, too. In fact, I've read that on some of the less honest blog websites, the owners fill their own forums with phony posts to make it seem like the website is more relevant than it actually is.
Did you ever wonder how an issue like illegal immigration, or Terri Schiavo, or Harriet Miers blows up seemingly overnight into a big internet-driven deal. The fringe groups have learned how to use the internet to flog their agenda items, and they often use truly dishonest techniques to do it.