[quote author=“sleepygeek”]The unlimited data plans are one reason iPhone isn’t 3G; one way to cap use is to lower the data rate. But the unlimited plans were vital to Apple to kick start the mobile internet. I’m fairly sure the “unheard rates of data traffic” per user will moderate somewhat. The early adopters are the heaviest users.
I also don’t see this as so big a problem as the networks might pretend. What it’s going to do is drive adoption of more wifi in high density areas. In low density areas, users will just learn to live with contention and slow response. In other words, investing in the GSM data infrastructure isn’t the preferred way to handle the growth of the mobile internet.
A voice of reason. 
This certainly becomes less of an issue as wifi becomes more common. There’s too much worry IMHO about the release of a 3G iPhone. The costs of infrastructure is more reason Apple is choosing exclusive carriers. The more concentrated the revenue stream, the more economically feasible the investment becomes for the chosen carrier.