Well, Perforce in its default state may not scale sufficiently, but at least two of the companies on that list have managed to make it work (presumably with a lot of investment, though). :)

I didn't know Amazon was using Perforce. I interviewed someone from Amazon recently and he indicated they were on Git for most things now.

Amazon has phased out perforce a year ago. There is very little left, most repositories (perforce, svn, etc) were migrated to git repositories.