At The End Of One's Tether
Many carriers, most notably AT&T, but also others such as Optus, are getting a lot of bad press for charging their subscribers extra for "tethering" their iPhones to their laptops.
This does seem to be blatant gouging on their part, given that bytes are bytes, and regardless of whether they are destined for a phone or a tethered laptop, the cost is the same. This criticism is warranted in my opinion.
Carriers may claim that tethered laptops inevitably draw more traffic from individual subscribers. But I would suggest that the incremental traffic from a tethered laptop is a lot lower for the iPhone than for other 3G phones. Let's face it, the iPhone is a pretty capable standalone device, and you'll rarely need to break out the laptop to get online. Other phones are far inferior at browsing the net directly, and so I'd expect that there is a correspondingly larger proportion of traffic from tethered laptops of subscribers with these phones. This makes the additional pricing seem even more unfair.
But not all of the hate should be directed towards the carriers.
I am yet to see an answer to this question: how do the carriers know which traffic originates from the iPhone itself and which from a tethered laptop? I don't know the answer definitively but I the iPhone must mark the tethered traffic somehow. I'm guessing that it must pass through the PPP session from the laptop, instead of terminating it in the phone and NATting the traffic.
Regardless, it is Apple that deserves at least some of the blame here for enabling the carriers to detect traffic in the first place. I know of no technical reason why they needed to do this; it sounds like a purely business decision. And one they didn't need to make; surely the carriers are all Apple's bitches at this point?
Boo, carriers who charge for tethering. Boo, Apple.