good point. StackOverflow used physical boxes not virtual servers and that certainly makes scaling a database easier. On the other hand I currently host HireFlo on a single Rackspace cloudserver. I have 3 web apps, a SQL server instance, and 2 processors hosted on the same VS and it's working well so far. I'll definitely move SQL Server off to it's own box at some point though.
As for the sysadmin on the software side, I agree most .NET devs that want to build something probably have those skills. It's the hardware aspect that I think needed to be addressed.
The OP espoused the easy scalability of .NET using the Stackoverflow example without mentioning that they colocated with dedicated hardware.