i do not know much about metropcs but do have a cell phone store that largely caters to cricket prepaid customers.
i will say that these customers tend to be extreme heavy data users with the emphasis on videos and music. also most of these customer do not have home and/or work wifi to fall back on.
this is quite different than the contract customers i know who tend to have and use a home internet connection via wifi and overall are much lighter consumers of streaming music and video from smartphones.
if companies like metro and cricket experience extra heavy network strain i is certainly no surprise to me, but they should really get rid of the 'unlimited' marketing and advertise the pre-throttle data allotment.