cell phones on airplanes

Everyone knows that when you fly you're not allowed to use your cell phone for the majority of the time that you're on the plane. I always wondered what the actual reason for this was, and how dangerous it could really be. There are interesting blog posts on Slashdot regarding this.
One of the reasons stated for this is that it gives the airline the ability to manage the crowd better, especially in the case of a dangerous incident. This makes sense, because even on a standard flight with no problems, a certain amount of cooperation is needed between the customers and the workers. The same person said that the airlines also like to keep passengers ignorant about the ground conditions.
Other arguments were that it was a way for the airline to make more money from the phones provided in each seat and that a call from the air would require the phone to use up too much bandwidth from too many cell towers.
What the public is generally told is that a call could interfere with other systems on the airplane.
I think that if cell phones really were a danger, passengers would not be permitted to take them in their carry-on luggage. Everyone seems to have their own opinion on this matter, but I'd be curious to find out what the real reason is. Either way, I don't think that it's too big of a deal to not use a phone for a few hours.