Microsoft announced that we announced “As of November 1st, 2010 we’ll discontinue support for the Bing Search API 1.1. For those of you’re using older API, you’ll need to switch over to newer Bing API 2.0 over the course of the next 3 months. To help make the switch to new API as easy as possible, we’ve developed a number of resources linked below. This includes implementation instructions, code examples, links to forums, and other helpful resources,” informs Microsoft.
Bing Search API 2.0 was released in June 2009.