It does actually say in the T&Cs that it's going to use you as a p2p node if I remember rightly, it's been a while since I've seen the header but it was listed as 'Computational resources'.
It's really getting to the point where T&C should be standardized and any extra conditions they want to throw at you should be presented front and center.
Yeah, and everyone reads those.
Well, you are kinda meant to read them. If you say you've read and agreed to something you don't have much scope for whinging.