I think the tempo is going to Yahoo on the API front.
Rather than write the crude attention grabbing title: "Yahoo is kicking Google's Ass on APIs", I decided to use the symbol for "much greater than". Anyways, here's the intial proof: the Y! API Wiki now has about 15 apps from third parties listed. Cool.
The Google AdWords API guys did announce a service to manage account settings. So maybe Google is going after functional completeness for the pro developers, while Yahoo's late launch allows them to get the net-buzz excitement. If that's true, it's an inversion of Google's usual approach, I think.
How about a contest, or a wiki Google?