Googles answer: Google believes that feed-based content and advertising is a developing space where we can add value for users, advertisers and publishers. FeedBurner's technology and talented team are a great addition to Google's current solutions for advertisers and publishers. http://www.feedburner.com/google
The main goal of Feedburner is to provide RSS and with that advertisement. Google main source of income are ads, so the acquisition of Feedburner is not so far fetched.