Tethering?

Has anyone heard of the technological phenomenon called Tethering?

Recently, a friend explained to me that I could use Bluetooth or a USB Cable and suck the broadband internet connection from my Blackberry Curve to use on my Labtop. This is ideal for people traveling that want to connect to the internet through their computer rather than through their smart phone.

However, I am more than positive it does not work on all smart phones. When I was on the phone with AT&T recently, the customer service representative said it would work with my Blackberry Curve. Though, my brother explained to me when he stopped by the Apple store over the weekend, that the Sales Consultant said tethering would not work with the present iPhone 3G.

I have not yet tried tethering, but I would speculate that many of the Internet Service Providers do not like the sound of this. If this is the case, these companies face the question of whether to charge consumers for tethering or to lose out on further revenue growth?