Scalability shouldn't be a problem. Stack Overflow uses ASP.NET MVC with a SQL server backend, and they're doing over a million hits a day.
Add one or two orders of magnitude, then you're talking about scalability.
Moreover, a hit is a rather arbitrary unit of measure. 11 hits per second to the Twitter API is a lot different than 11 hits per second to a static site like example.com.
There's not much point even taking that into account for a read-only affair like SO at such a small scale because the cache is doing the work here and that won't sweat even under 100 or 500 reqs/sec.
Anyways, you point out correctly that discussing scaling-issues is rather fruitless without taking all variables into account. I was just trying to say that "SO (in particular) is handling 1mio reqs/day" does not tell much about the performance of the underlying stack.
Yeah, why solve problems that you actually have when you can fantasize about solving problems you don't have instead?
However, the whole topic of this thread is fantasising about the perfect stack for that massive site. Besides which, 30 seconds now could save one year in the future (just think if Netscape had thought ahead).