Let's do the math:
400,000 units divided by 50 states = 8000 PS3s per state.
Figure 3 major cities per state, = 2,666 per city area.
Figure that there are 50 stores per manufacturer per large metropolitan area, say Target, WalMart, BestBuy, CompUSA, CircuitCity, Electronic Boutiques / Gamestop / Babbages, Cosco, Toys-R-Us = 400 stores. (How many Malls in your city?) 2666/400 = ~6 per store.
Now, a lot of people may be thinking that 50 stores per manufacturer is a high number. Until you figure that Boston includes a lot of surrounding cities, that NYC is the 5 boroughs along with all the cities in Long Island and Yonkers & Westchester, that the surrounding area around Philadelphia probably includes 30 smaller cities, that Dallas / Fort Worth also includes Arlington, and that L.A. is a really big place. I figure the easiest place to find them would be Las Vegas.
So basically if you go to a store and see more than 7 people on line - you might just as well go back home.