Another answer is it's because most startups are consumer web-focused and MS traditionally hasn't been.
ASP.NET was traditionally an enterprise framework. Which got long in the tooth. ASP.NET MVC is quite good, but probably just caught up with the leading FOSS with MVC 3. Give it a year. And in general people aren't doing startups for desktops anymore, although they're still huge in the enterprise, which is why .NET is bigger in the enterprise than for startups.
The other big space for startups is mobile, but MS isn't big here at the moment. Why are startups using Cocoa now? Well because iOS is huge. If WP7 becomes huge, guess what happens? C# becomes a hot language for startups.
The author of the referenced blog (not the Piehead one) clearly doesn't understand that domains tend to dominate language. And further doesn't seem to understand that you try to pick the best tool for the job. A manager begrudging you for selecting the best tool for the job is not someone you'd want to work for.
Agreed. Distribution is the primary concern of most software vendors (big or small), so mobile developers are going to target Android, iPhone, and in some cases BlackBerry. Microsoft's mobile market share today resembles Apple's desktop market share back in the 1990s.
ASP.NET was traditionally an enterprise framework. Which got long in the tooth. ASP.NET MVC is quite good, but probably just caught up with the leading FOSS with MVC 3. Give it a year. And in general people aren't doing startups for desktops anymore, although they're still huge in the enterprise, which is why .NET is bigger in the enterprise than for startups.
The other big space for startups is mobile, but MS isn't big here at the moment. Why are startups using Cocoa now? Well because iOS is huge. If WP7 becomes huge, guess what happens? C# becomes a hot language for startups.
The author of the referenced blog (not the Piehead one) clearly doesn't understand that domains tend to dominate language. And further doesn't seem to understand that you try to pick the best tool for the job. A manager begrudging you for selecting the best tool for the job is not someone you'd want to work for.