3)Increased features - products are getting better all the time, and especially for electronics, chances are the latest model has some neat features that didn't exist when your couple-year-old broken one was made. So that's an added incentive to go new.
Some will argue that the throwaway society has been bad for other reasons - increased trash, loss of old-school charm, ect. The "landfill crisis" has been debunked by many, such as Bjorn Lumborg in the Sceptical Enviromentalist. And if people cared about old-school charm, they wouldn't vote with their wallets for assembly-line products.
So throw something out today - the throwaway society is a sign of how good things are.
posted by mad an