From a "control" perspective Perforce gets a lot of things right. It's fast, efficient and easy to maintain. It's also a big hit with nosy managers since they can easily limit what any developer can see and also tell exactly what each developer has checked out. Keeping all the metadata at the server has it's advantages.

I believe Perforce's customers include both Google and Microsoft. They must be doing something right.

That said, I think more and more people need to deal with multiple projects at once where there isn't a single central policy. Distributed VCS systems really shine as "control" becomes less important.

Have you seen any companies offering hosted mercurial?