Originally Posted by bkrownd

I don't know what universe you live in, but in mine the rear always takes more punishment and gets more flats, even with much tougher tires in the rear. (Actually, my front never gets flats even with cheap-o tires) Thus, the rear needs the more puncture resistant tire. If you find your front tire getting more flats than your rear maybe it doesn't work that way for you, but that would sure puzzle me.

Originally Posted by mikeshoup

Sheldon Brown has a good article covering tire rotation:
http://www.sheldonbrown.com/tire-rotation.html
What he says mostly makes sense to me. I like the idea of rotating front to back and put new front on.