It's probably not the stack I would pick and my initial reaction is always to gasp when I see startups built on Microsoft, but...<p>- ASP.NET can scale, if you do it right. Aside from Microsoft.com/MSN, which don't really count, MySpace uses it (though they upgraded from ColdFusion, which wasn't much better) and Plenty of Fish, the web's largest dating site, uses it too:
<a href="http://www.plentyoffish.com/about_team.aspx" rel="nofollow">http://www.plentyoffish.com/about_team.aspx</a>
These are probably all larger than the most successful Rails sites.<p>- ASP.NET MVC isn't a horrible programming model. Forget the abomination that's normal ASP.NET with its funky events. If you've used another MVC framework like Rails or Cake, you'll feel right at home.<p>- Microsoft's startup program gives startups the early software for super cheap: <a href="http://microsoftstartupzone.com/" rel="nofollow">http://microsoftstartupzone.com/</a><p>- It's all about getting v1 out and releasing early and often. If your team grew up on Microsoft, are you really going to make them all learn a new framework? If you do it right and prove out your idea, you can always rewrite later.