Sure, but having that information is not the same as being able to utilize it. I can't look up everything I buy every day, nor would I really want to. It makes things easier if I can basically trust that people aren't trying to rip me off. I think in most markets, it's in the interests of the vendors to not attempt that, but still, it's an interesting question, and I'm suspicious of all-or-nothing answers on any side (the market/government should take care of everything).