Filter imported posts by taxonomy

I have feeds running on a rather large site with many feed nodes importing blog posts coming from all over the place. Right now we're trying to get users to make custom rss feeds for only the content they want to have imported. This is proving too difficult for many users (or they're just lazy) and we end up importing all their blog posts.

I think it would be interesting if I could come up with a taxonomy tag "mysiteisthebest" (or something just as creative) and have feeds check for this in the imported nodes and only save the new node if it's there. I might be able to tackle this but is this interesting for anyone else?