Wanted to use it with Google Analytics for a kind of recommendation engine of the form "users that liked this page also liked...". But they never approved my request and a 60k request limit won't cut it either.
I'm using it in an app, since my request did get approved, but it's very rudimentary at the moment as I am still exploring it. I'll be sure to report back to HN at the point it is in full use.
