The API we're using for play history currently isn't something we're
comfortable exposing. We are working on a new play history system that will
be more performant (good for our users) and will be sane enough to expose
through our API (good for developers).
I expect that this new API will be available in the next couple of months
but I don't want to make any promises - it's taken longer than I'd expected
to get up and running.
*Ian McKellar*, API, *Rdio Inc.*