It seems logical that you could hotspot if you have a finite data limit. Hey, you hotspot and use it up faster, you'll buy more data more quickly! I do wish more places had data that would last more than 30 days like T-Mobile does. I have T-Mobile on my phone-- just looking for a secondary provider for those fringe cases where I have no service with T-Mobile. (I only get like 50mb of data roaming onto AT&T's network... and my phone will chew through that in no time without me even thinking about it.)I'm grandfathered to a Mobile Share 20GB plan ($100 20GB + $15*4 phones + $10 tablet).
I think we use around 15GB a month (normal web use, music streaming, laptop and wifi-only iPad tethering but little video streaming). Funnily enough, back then, mobile hotspot was $20/mo while tablet was just $10/mo so I opted for the tablet.
I do have iPads on the $10/5GB/150 day T-Mobile Prepaid Pay As You Go plan and surprisingly, it supports hotspot.