Bob Metcalfe (inventor of Ethernet, founder of 3Com) over the years (going back to 1994 or so) has raised similar concerns about flat-rate Internet access. Bob has said that all-you-can-eat Internet compared to per-megabyte isn't going to scale well, and will gridlock the net. Making people pay as you go is the only way to keep it sustainable.
Bob's been proven pretty wrong. I think.
And as for Mr RIM, I think he's wrong too. We didn't get from the 957 to the 8700c only because of RIM. It mostly happened because of customers demanding a better (faster) network, and suddenly being able to do more things with a phone/handheld on that network. The carriers built it, the customers and RIM came, and with enhanced EV-DO, HSPDA, etc., it's only getting even more robust and flexible.
If we were hobbled either with Rogers-style data charges, or Mobitex-only data, people wouldn't bother with traditional carriers. We'd lug laptops around, wardriving or paying $6/hour for a T-Mobile hotspot.