I might be misunderstanding the concept completely, but here's the question: when I try to add a blog's feeds (the blog is hosted at Blogspot, so it provides both Atom and RSS) to FeedBurner, it suggests to choose one of the feed formats. Is it possible to track subscribers of both the both feed formats? Thanks.
FeedBurner takes your source feed and populates RSS and ATOM feeds on its own site.
?format=atom to the end of an existing RSS feed hosted at FeedBurner for an example.
It looks like the result is an aggregate XML document which uses a variety of formats:
<rss xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:wfw="http://wellformedweb.org/CommentAPI/" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:atom="http://www.w3.org/2005/Atom" xmlns:sy="http://purl.org/rss/1.0/modules/syndication/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:feedburner="http://rssnamespace.org/feedburner/ext/1.0" version="2.0">