Just wondering, how many users/usage can a set up like the one in the article handle? (For example, how many concurrent users for a web app that's a social networking site with mostly news feeds, comments and some pics?)
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...