Blog Advertising: Is it Really Worth It?

Many companies choose to advertise on their blogs once the community reaches a considerable size, and when it has a decent amount of pageviews a month. I came across this post from the Inquisitr which highlights how most ads are paying less than the benchmark $1 CPM, let alone the spammy ads which deliver 20-30c CPM.
There is a lot to choose from when searching for an online advertising broker, but not a lot pay well. Searching through comments and recommendations from peers, we've come across at least one company which seems to be a winner, Project Wonderful. Project Wonderful uses an auction system to figure out what ads go up on your page, and of course, ultimately the user has final word on what goes up. What are some other examples of ad companies that you have used in the past? What's your take on advertising on blogs?