Folks like Sony and Microsoft have been around the block. As a business, they are likely much more organized and have more resources than what Nintendo would have access to. So while MS or Sony could open up a whole new factory to mass produce more systems to fulfill demand, Nintendo may not have that luxury--regardless of the current success of the system. Both Microsoft and Sony can pull resources from other parts of the company (though I'm sure the games division has their own budget) when they need to take care of something like this, Nintendo is currently a pure 'just games' company.

Besides, I've had situations in my job where all of a sudden, one item starts selling like mad. So I order 3 times what I would normally order for stock, and then the items do not sell. I'm stuck with a lot of dead stock.

I'm not saying Nintendo will end up with dead stock of Wiis, but if they spend the money to make more 'Wii-making machines', what happens after demand drops off? They have more 'Wii makers' than they need, and they can't really use them for anything else (whereas Sony could hypothetically rewire them to make some TVs or something). It's impossible to predict what resources they would need to keep up with future demand, and whether or not that demand will sustain for a while.

Unless they do in fact make enough money to stop time.

Edit: As for Console Sales Charts, I trust www.vgcharts.org a lot more than 'nexgenwars.com'. They've been around longer and have a pretty good legacy behind them. Use both of them and compare accordingly.