Botnets moving beyond spam and DDoS

With a conservative botnet size of say, 10,000 computers, what else can an attacker use it for? One popular approach (understandably so) is to use the botnet to make easy money. Advertising networks, such as Google Ad-Sense, pay publishers of banner ads on a per-click basis. Depending on the advertising network, prices start as low as $0.01 per click and go as high as $0.50. An attacker can unleash their botnet on a banner ad page consisting of, say, 200 ads, and at $0.01 per click they can easily make a $20,000 profit. Obviously, the larger the botnet, the larger the potential profit. Moreover, if attackers find they have more than enough bots, they can rent out their botnet on the black market for as much as five cents per bot, per hour.