There has been plenty of news about data traffic growth caused by iPhone popular overloading networks in the USA and more recently the UK.
I have been in Northern Italy for the holidays using 3 Italy's 3Power10 pre-paid SIM for the duration of my visit. I was quite surprised with the incredibly slow performance of their network after my positive experience with China Unicom's brand new 7.2megabit HSPDA network in Guangzhou.
On China Unicom in South China, where official iPhone sales have been off to a slow start, I get download speeds ranging from 800 kbps to 3.5+ megabits consistently averaging around 1.9 megabits. In Northern Italy on 3 Italy, the range is from <10 kps up to a maximum of ~1.1 megabits. Averages in Italy, however, are quite low around 100 kbps. Perhaps this has something to do with the fact that every other person on the street seems to have an iPhone?