Of course you can, but circumventing the way IMPOSED by Blizzard to play the game (as in the game and itemization was built around the existence of the auction house) you'll find that you're hindering your own progress for no reason.
I'm a smoker. I tried to quit. Never managed to because cigarettes are everywhere around. Now, if we're talking 10-15 miles between me and them, then fuck it, I won't bother. Some would, but I wouldn't. The best analogy I could come up with between D2 and D3 trading system.
Edited by Sartorius, 09 January 2013 - 11:37 PM.