As webmasters, we have a built in patience and ambition for learning how our own sites work.  The average user won't have that  patience and ambition.  If they can't figure it out immediately, they're gone.  You'll see them register an account, then you'll never see them again.  No one gets a second chance to make a first impression.

I hope everyone is taking notes about now. Your average user is looking for simplicity. His or her view of a site's usability is this: "Don't waste my time and make me wonder. Don't make me wonder what you possibly had in mind to make things so confusing."