Anandtech explores the validity of Apple's decision not to use 3G wireless network technology in the iPhone.
Jobs' explanation for not using 3G in the iPhone came down to issues with size and battery consumption:
"When we looked at 3G, the chipsets are not quite mature, in the sense that they're not low-enough power for what we were looking for. They were not integrated enough, so they took up too much physical space. We cared a lot about battery life and we cared a lot about physical size. Down the road, I'm sure some of those tradeoffs will become more favorable towards 3G but as of now we think we made a pretty good doggone decision."
Anandtech disects a Samsung Blackjack as well as the iPhone to compare chipset sizes for 3G vs EDGE implementations and concludes that indeed the "iPhone would have to be a bit thicker, wider or longer to accommodate the same 3G UMTS interface that Samsung used in its Blackjack".
They then proceeded to try to determine exactly how much of a battery life penalty the Blackjack suffered from when using its 3G network. The comparisons aren't direct, but they were able to determine the relative usage penalty on the Blackjack itself (3G vs EDGE) and compared to the iPhone's (EDGE vs Wifi).
In the end, 3G network usage on the Blackjack caused a 23% battery life reduction in using 3G vs EDGE to browse web pages. In contrast, iPhone's EDGE implementation produced a 25% battery life reduction compared to its Wifi implementation. This would suggest an even more substantial battery drain on the iPhone (relative to Wifi) if it did implement the 3G network.
A more interesting observation was that simply leaving the 3G network enabled on the Blackjack reduced the Blackjack's talk time from 9 hours to slightly over 4 hours. They conclude that the iPhone's talk time would be reduced to less than 3 hours of talk time if its battery was similarly affected by a 3G implementation.