It's 2010. Checking to see if a patent is still valid is trivial. What happens to old stock or whatever? Do retailers have to pull things from the shelves when

It's 2010. Checking to see if a patent is still valid is trivial. What happens to old stock or whatever? Do retailers have to pull things from the shelves when their patents expire? Better yet, you could have a product code, that could lead to a web page that has the list of patents (and potentially other information; recalls etc?) on it.