Best way to implement a "favourites" container

[timster]

My library has gotten quite large, and I've never been a fan of ratings, so is there an easy way to implement a favourites-type container? I was thinking of a custom tag "favourite" that I could set for particular albums or even tracks (so it would either exist or not), and then the container would be top-level "Faves" or something, and only contain items that have the tag.
Is this possible? Or would it contain another container with the value of the tag and the items in it, and another with <unknown> for those without the tag?

Or is there a better way?