I think it's too late for FeedBurner to go after MyBlogLog.
FeedBurner and MyBlogLog come from very different directions but are ultimately marching towards a meeting.
MyBlogLog lets you see who has been on your blog; either through standard web metrics or the canny photograph log. You also use MyBlogLog to help promote your site.
FeedBurner allows users to look after RSS feeds and track who is reading them. By an overwhelming majority most web sites that issue RSS feeds are blogs or blog-based platforms.
In essence MyBlogLog gives you stats about who is actually visiting your blog and FeedBurner gives you stats on who is viewing your blog remotely. FeedBurner would be enhanced with improved on-page tracking and if it had a quirky social media promotion style feature. MyBlogLog would be enhanced if it worked with RSS feeds. Most people subscribe to their favourite blogs via Google Reader, Bloglines or similar external source.
If MyBlogLog gobbled up FeedBurner then they would end up with a nice user base, Yahoo would have some tasty data to crunch through and a large database of RSS feeds.
As it happens Yahoo has a patent application called Integration of personalized portals with web content syndication. Yahoo could do a lot with a database of RSS feeds. This particular patent describes how the search engine first identifies pages with RSS feeds, presents that information to searchers and then allows users to add those RSS feeds to a personalised portal. This personalised portal is Yahoo's MyWeb. However, the personalised portal could so easily become a profile page on MyBlogLog.
My feeling is that FeedBurner is more robust than MyBlogLog. MBL will have to innovate and impress in order to avoid being a flash in the pan. Yahoo clearly has some ideas for it. I just wonder whether they are thinking along similar lines.