Couldn't the same argument ("just a VM and a set of APIs") be made for many programming languages, Web or otherwise? I'm not criticizing what you wrote, just trying to make sure I understand what you're saying.
Gotcha. I'm just arguing (mildly, 'cause the most .NET experience I have is a two-week project a couple years ago) that possibly .NET and friends is not the best choice for a massive site such as MySpace, at least if you are not prepared/qualified to completely reinvent the wheel (as you seem to have done). Then again, Facebook's solution seems pretty ad-hoc as well. Perhaps such wheel invention is inevitable.
Yeah I see your points. I just wanted to point out that ".net" is different than asp.net and IIS. Those are part of the complete default stack and are typical bottlenecks. In a way they're designed to achive easy development/deployment over performance.
asp.net out-of-the-box will not work for a massively concurrent public facing app. However, neither will php, rails, django, any of the java frameworks. "re-invent the wheel" might be an overstatement for what you need to do, but no matter what...you're going to do some serious tweaking since every app has different needs
