I know at Target, the Wii is generally not advertised unless there is a planned shipment on the way because company policy is to keep all advertised items in stock, at least when the ad goes into effect every Sunday morning. To advertise the Wii without any chance of having some for the Sunday opening (or at all throughout the week for that matter) would give people the wrong impression, it seems.
Games, of course, can still be advertised, but the console and primary accessories are not shown unless they will definitely be available.