I'm using both Zemanta's article recommendation and their in-context program. It is an extremely cost-effective way to get links if you a publisher. You'll need to have a baseline level of articles or other information-rich content types in order to succeed.
Note that with Zemanta, you pay for the impression with the blogger—the blog still has to choose to include your recommended link. As a result, you control your own destiny with Zemanta, as your cost-per-link will be a function of your content quality.
