To 'monetize' or not to 'monetize'

The real questions are:

1) How much money can actually be made by 'monetizing' a blog?

2) Is it worth gunking up your blog with a bunch of distracting billboards?

I personally don't like to see a bunch of distracting adverti$ing plastered all over the place.

So for me, there would have to be a lot of money in it before I'd be willing to allow the adverti$ers to hijack my blog.