one or more
Jim Lanzone from Ask posts some some interesting stats to their blog about "what feeds matter." I'm sure this will spark all sorts chatter about index size and audience size and power laws and all the other usual topics related to blog indexing, blog search, audience size, etc.
But I thought I'd point out one interesting thing in Jim's analysis: his definition of a feed that matters is any feed with at least one reader. Even though "one or more" may not be a terribly useful filter if you're a buyer of site-specific advertising, there's something simple and elegant about the statement that "if it matters to one reader, it matters." It's a reminder that the long tail has the potential to become very, very long.