Botnets that make money, but at who's expense?

The article is locate here.

Witlog claims he doesn't use his botnet for illegal purposes, only "for fun." I found that claim pretty hard to believe given a) the income he could make installing ad-serving software on each computer under his control, combined with b) the risk he is taking of getting caught breaking into so many computers. The kid I wrote about in the Post magazine story on the connection between botnets and spyware was making $6,000 to $10,000 per month installing adware on a botnet half the size of the one Witlog claims to have.