I visited Best Buy today and there was literally a mountain of GH and RB full kits. It was ridiculous how many they had. I estimated they had at least 300 full kits. Honestly, I've never seen anything quite like it. They had 8 foot high stacks all along the front of the store, so much it felt claustrophic walking amongst it.

And they hadn't received RB2 Wii yet.

With the PS3, XBox 360 and PS2 versions of these games I have seen the same thing but until yesterday I had never seen a full Guitar Hero World Tour kit for the Wii ...

You didn't see the stacks of PS3's they had around last X-mas?

It was like that at Fry's Electronics too. The overestimated how many people would by for the holidays. Those $130 - $180 box sets aren't going to sell that well. Too expensive and people has to buy lots of give for many people. Because Rock Band Guitar Hero was so popular previously, retailers though that stuff would sell like crazy, but they were wrong. They'll  have overstock for at least 3-4 months after the new year I bet.

Stores have been stacking them in crazy amounts since Rockband one came out. I've seen pillars and some sort of home/fort made out of them in a Future shop.

imagine how high the Wii versions number would be had they shifted some of those orders to the Wii version.

It doesn't matter if they don't sell right away, they will sell no matter what. If not, they'll lower the price slightly to get rid of stock. Problem solved.

I've seen mountain of ps3 version in my local target.

This isssue is how much it will cost. If it takes up floor space for weeks or months and they have to discount, it could lose money for the retailer.

It's always like that cause they know they will sell them sooner or later anyways.