A study of 55,000 cell phone bills from ATT and Verizon strongly suggests that data throttling is useless, and instead a ploy to move customers to more expensive tiered plans. The money quote:
"Validas raises the question of whether the carriers were throttling simply because they want unlimited data customers to switch to limited, tiered plans. It is a befuddling question because it could potentially cost customers more over time. After all, how can a network be out of capacity if it can serve a customer on a limited plan without throttling if the heaviest data users on both limited and unlimited plans are consuming roughly the same amount of data?"