To be honest it's impossible to tell without actually measuring it. The #1 rule of scaling a system is to measure the variables your trying to optimize, make a change, and then take measurements again. So without knowing the kind of software that's running on this we have to leave everything in terms of a theoretical workload.

If you aren't doing graph operations, then 50 dedicated servers can do a pretty impressive workload. Add in graph-ops and all bets are off :-). The same could apply for user-generated content (eg youtube, facebook, vimeo).

Stackoverflow is another great example of a company that vertically owns their stack. Check out:

http://blog.stackoverflow.com/category/server/

http://meta.stackoverflow.com/questions/52353/how-many-serve...