The RIAA and/or MPAA seem to have cottoned on to the existence of IRC, and now have machines that trawl IRC, presumably for fserves. Of course, they don't do it obviously, but instead use anonymous bots which regularly change through nondescript names.
I'm on a channel which I use to keep in contact with my uni friends, on Quakenet. It's fairly close-nit, with regulars, so we tend to notice random people who pop in, say nothing and then leave. I used to think 'how rude', but then I noticed that some were the same IP repeating. It appeared to be a bot which kept joining, but doing nothing... so I thought I'd investigate (eventually). And then I noticed there were at least a couple which'd been popping in: