I can see you did not think about it for one moment. If you did you would realise that if every other mobile maker, especially the giants you refer to, did the same then the networks would loose a massive stream of revenue. If you could bring yourself to think that far you would see that the business model is flawed as soon as the user base becomes too big.
Either it needs to change and everyone should be offered an uncapped connection, in which case blackberry is stuffed. Alternatively blackberry needs to make their services work on normal internet like all other makers does, in which case blackberry is stuffed.
Basically if it gets to big they are history.