And that's pretty much why Google built Google Web Designer[0] - because advertisers are going to want their media to run on all browsers, even ones without Flash.
I do all my rewriting with a proxy (in my case glimmer blocker, though I also had to implement my own man-in-the-middle SSL tool to make it work with https connections). I simply rewrite URLs, strip referrer tags, respond with empty files for domains I don't like, and rewrite pages to remove crud. It speeds up my browsing experience immensely and coincidentally improves my privacy somewhat.
I seems brain damaged to me to do it via a browser extension since I use multiple browsers, not to mention other programs that make http/https/ftp connections (e.g. RSS reader, mail reader etc).
