Strong examples of technology startups (or stays) with .NET?

Question

I am looking for specific examples of vivid, attractive (or acquired) technical problems, especially startups who decided to build on the Microsoft stack and either succeeded, or most likely turned out to be.

Writely is an obvious example, as are NewsGator, PageFlakes, and StackOverflow.

I do not want to say that this is a discussion in the language. Hope this question is not too subjective for SO; I and the team I work with have greatly benefited from solving the coding problems that can be found here, and I expect that the people who can best answer the question often visit this site.

To make the question a little more specific, let's say you are a .NET expert and a member of a startup that is at a turning point. This turning point may or may not include a shift in the platforms. Avoiding subjective arguments, what quantitative examples — companies or case studies — can you point out to go or stay with .NET? (Additional examples for examples in the Valley.)

Answer 1

I would recommend looking at the Microsoft BizSpark Launch Directory .

This shows that most new startups use BizSpark (which will be intelligent using Microsoft technology). Most of them are probably .NET oriented.