dug 
http://www.appleinsider.com/articles/09/09/03/bandwidth_guzzling_iphone_called_hummer_of_cellphones.html
The average iPhone user reportedly consumes 10 times the bandwidth of a typical smartphone user, but that is expected to change in the near future. The growth of the iPhone and its impact on the AT&T network has even led to lawsuits. As other mobile devices emulate the iPhone and also use more network capacity, the problem is expected to grow on all networks, not just AT&T.