orkut is still in ASP.NET. While Google as a company is a big proponent of OpenSource, they also encourage their engineers to use whichever tools suit their needs, whether OpenSource or not. Ultimately, Google as a company woulf PREFER everything be written in one language, but to enforce this in an engineer’s 20% time would be counter-productive.
orkut.com is an example of this. It was originally written in ASP.NET and is still to a large degree ASP.NET driven, though it uses some wrappers to make it more scalable in Google’s architecture.
As for someone saying that AJAX is all about Javascript for server-side requests… while that may be true for the REQUEST (which is handled on the client-side)... the actual RESPONSE (processed on the server-side and sent back to the client) is not likely to be written in JavaScript. In other words, the JavaScript portion of AJAX is only on the client-side. There is no standard for the server-side code for AJAX processing, so it could be ASP.NET or python or any number of other server-side languages.