Many already do.
With Slingplayer thru Wifi or on a JB iphone with 3GUnrestrictor that lets your stream thru 3G/Edge.
Also OrbLive streams live TV thru 3G, Edge and wifi.
Yeah and it rocks. Was watching bblb while enjoying my big mac meal yesterday. I use a windscreen holder and 3.5 jack to my stereo so audio is good to. It's been more Stable on 3g aswell lately. Just hoping it lasts .
There are many options for live TV on the iPhone. I had it on the original 2g with Orblive. If you can run cable through your computer, you can stream it to your phone. It's a cheaper alternative to the sling player and it works very well.