I also heard that it is in the area of 1$ per 1000 views, but varies greatly.
Anyways, if you have a few thousand views a day, you could end up making some money off of it. If you only have a hundred views per day (like me), the 3 bucks each month in my opinion don't make up for the 5 second ad the viewers have to sit through to get to your content.
I think you really have to balance the money you make from it versus the annoyance of your viewership. I never turned on any ads, since when I send friends a link, I don't want them to watch an ad first. I'd rather have them pay me the 0.1 cents directly. 🙂
Just some thoughts...