Or, it could be the bleedingly obvious...
As to the throttling itself, intriguingly it is not consistent across video providers or operators, suggesting that there may be deals between certain mobile phone networks and certain video streaming companies to let their videos pass through unthrottled.
Or, some of the throttling is actuallly due to periods of congestion, which means it's not at all throttling.
I would love to understand how the researchers controlled for the natural mechanisms of the mobile video client to negotiate video quality. Not all phones or apps are created equal, and some like Skype are clearly nothing but utter shite at this stage.