I actually don't think this is particularly heinous as long as they are completely transparent and open about it. Hell, if they wanted to be even more above board, they should provide a slider that allows you to allocate a percentage of CPU usage you are dedicating at a given time.

Now, whether it'll be worth it is the real question. But I'm hopeful. If we can find an alternative to obtrusive, obnoxious ads I'm all for it.