After encountering a number of problems trying to filter Blogger feeds by tag (using services like Feedrinse and Yahoo Pipes), I’ve finally put together a solution that works:

• Shadow the feed with Feedburner.
• Enable the Convert Format Burner, and convert your feed to RSS 2.0.
• Use Yahoo Pipes to filter the feed (because Feedrinse seems to be broken).

This let me create a feed that excluded all my posts containing the fbpost tag, thus allowing me to avoid yet another postgasm in Facebook when adding new import URL to notes.