We seem to be up at the moment, but we had a flood of traffic around the MacWorld Keynote this morning. No surprise, of course, but since we couldn't move data centers earlier this month we don't have many machines to throw at the increased load.
In the meantime, I've drastically increased the API rate limit and disallowed unauthenticated requests to the API. This is temporary, and once our load decreases later today things will be back to where they used to be.
Thanks for your patience, and enjoy the Apple fanfest!