This question is a result of a discussion with someone else.

Is there an ad network that will serve up ads (both text and banner) bases on what the blog post is about?
EG: I blog about the latest tech gadgets.
And bam, on the sidebar for visitors to see are ads about tech gadgets.

Now I know there are ad networks (I use infolinks) that will put in-post ads based on keywords.
They are alright, but if I have a blog post about tech gadgets, they serve up insurance ads, cruise line ads, etc, based on the keywords found in my post.
Not at all about tech gadgets.