What powerboatr said.
Rubber is not sandpaper, you aren't running it in one direction since you are constantly turning and encountering different surfaces (asphalt, concrete, etc).
I do not sell/buy/have shares/do anything with tires so I have no reason to have people rotate their tires so that they buy new ones sooner. If rotating your tires is such a bad thing why does ford, or anyother dealer for that matter suggest doing it to maintain tread life and wear? Think of it this way, you write with your pencil and if you keep going at it on one angle, it wears away down to the wood and then barely writes. IF you turn it, it will write nice, sharply and crisply. Similar to the tire... if you leave it on one position then it will wear down part of the tread and then you have to worry about blow outs and reduced handling. I could go on, but NOT rotating your tires is NOT a good thing to do. I'm not going to get into a pissing contest but for the sake of the original poster, it is good to rotate your tires. (added bonus, you find out you have a leaky axle seal when you remove the tire and see the newly painted inside wheel. Save yourself alot of money so you don't have to get new gears because your old ones burned out from lack of lubrication!)