This one is my favorite:

Customers only know what they want after they see it.

But these are good too:

The entire software industry is built on top of wild ass guesses.

Quality is best measured at the customer.

My job is to lie to customers, your job is to make me look good.

The last one is a quote from a sales person. This is always a bad relationship to have with your sales people and is usually an indication that you're in a toxic work environment.

http://thecodist.com/article/lessons_from_a_lifetime_of_being_a_programmer