Google Buzz API - Google Code
code.google.com
code.google.com
While it was a huge loss for privacy when they actually did it, (and seemed more like not thinking than anything else), once I turned on settings to block people, it was easy, everyone was there, and already using it.
I always wondered why they launched without a complete API. one thing that made their competitor Twitter so popular was the availability of all these different clients optimized for various needs.
The strong geolocation support in buzz made it really suitable for posting pictures for example - pictures that then would appear on the map around you.
There was no API and the web client didn't support it due to it being optimized for the iPhone which has no file system and hence no upload support and the api didn't exist, so you could not write your own client.