That wasn't just an idea. People have used Twitter for exactly this purpose for a long time, because it skews user numbers. I'd also assume that overhead is very low for c&c botnets, since its ultimately just a little pubsub message queue, so there's even less incentive to shut them down. I get at LEAST three followers a day with "buy RTs, followers" in their profile on my personal Twitter.

Spam botnets ain't nothing new. They'll ways be around.