Onvia's new policy is largely due to their high number of returns on the Sony G400 monitor (which they dropped BTW). See previous threads on the Sony, it's been a nightmare for Onvia.
Re: Defective pixels. Depends on the manufacturer. Some accept a certain number of dead pixels, others do not. Viewsonic and Mitsubishi accept a certain number of them, and it depends on which region of the screen they are located. Sony does not accept them. Can't say for Samsung or KDS ...