Even 5 seconds sounds insane to me.
I’m willing to give companies like Facebook a few hundred more milliseconds since they sometimes have to do non-trivial computation, but somehow Google manages to stay more or less within my performance expectations.
I really like most of this article, but I’m concerned by a) the arbitrary five-second budget and b) the glossed-over vagueness of this model of the median user. Besides which, is it acceptable to ruin the user experience for half the audience? And as @wyager mentions, what the hell are you doing that takes five seconds?