A couple days ago, Google quietly put a stop to a piece of history that was even referenced in many books. It was a classic example of how "web services" work, and was at the center of many mashups over the years. Unlike the "Google Answers" service that was let go a few weeks ago, its retirement doesn't appear to be welcome.
As Philipp explains, some are upset because they have built applications with the API, and feel that the discontinuation is like a slap in the face -- without so much as a blog entry to explain why it happened. Google has stated that there are no plans to completely close down the service, but they also told Camden Daily they were looking at "productizing" it about a year ago.
About this time last year, I was in discussion with some people on the Google API team and they seemed rather serious about ’productizing’ the API some time soon.