Thanks for the pointer. From what I can tell, it seems like you'd use Mashery if you were building an API for yourself, or for someone else? It seems to be more about the operations of the API that the strategy behind what methods the API should have. Right?

(From their company page, http://mashery.com/company: "We help brands... manage (their) API Powered Platforms..."

I'm not sure how much of each they do, though I'd imagine it's a bit of both, as obviously they're experienced in taking APIs public so they both have the tech to support it and the past knowledge of what users/developers want. Check out http://developer.rottentomatoes.com/ to have a look (it says Masher Made at the top)

There's also http://apigee.com/.

And for high-level guidance, http://redmonk.com/, kind of a Gartner for platforms/developers.