I'd think it would end up being sort of slow: your bookmarklet passes a url to your server, which gets the page, finds that it's a frameset, parses out the urls for the individual frames (converting relative and server rooted urls to absolute urls), and then gets all the frames and parses them one by one, looking for RDF.
And by the way, frames also prevent the bookmarklet from copying the text you selected into your post. And confuse people who think they can click a permalink and get the permalink url in their browser's address bar. All in all, not very cooperative with bookmarklet blog posting.