I just deleted about 600 spam accounts from the official 7-year-old Marco.org forum. They were easy to identify by their random or spammy names or email domains.
The interesting part is that the vast majority of these had 0 posts. It was a giant army of spam accounts ready to go whenever their owners wanted, but they were never used. I imagine this is so the spammer can go to clients and say, “I can get your message on X forums with PageRank Y in 30 seconds.”