I am on the pessimistic side regarding this.
My understanding is as following:
1) 200Mb free is "free" for their customers who is on a data plan or a voice plan. In that sense, the customer will be paying the plan. The 200Mb data will be free "for life", as long as one remains a customer with a plan.
2) however, if you look at their data plans (I did not study their voice plan), there is no "free" plan. The cheapest one is the "on demand" or pay-as-you-go plan. That plan is precisely $10 dollars a month.
3) To reiterate from point one and two, one can be a on-demand customer and get "free" 200Mb data every month. It is called "free" as opposed in the other scenario that you have to pay for both the plan fee and the actual on-demand data usage fee for that 200Mb data.
4) if I am wrong, and customer really indeed can get the 200Mb "no strings attached" data, then this "exceptional error" of T-mobile launch is a monumental screw up.
5) If I am right, this will just go down as another company now playing the rhetoric game and trying NOT to be forthcoming with their hidden charges.
just my 2 cents...
It seems like a screw up. If you look at the tweet again it say "Yes. Everyone gets the 200MB of free data. No exceptions. No strings attached." The last two sentences indicate that we should take '200mb of free data' at face value.