Tech for blocking particular YouTube video - Wired.com question

[Ryan Singel <ryan () ryansingel net>]

A colleague is working on a story that a particular country not to be named
implemented technology to block a particular infamous riot-inducing video
for a certain section of its populace.

The questions are: 1) how hard is this to do at scale, 2) does it require
DPI equipment and 3) is there a way to prove, from an end node, that it's
happening?

Off-list replies are fine, even better are folks willing to talk on record.

I appreciate any help you can give.

Ryan Singel
Editor
Wired
Threat Level