The only way that users won't say that is if the "Windows for Netbooks" is lousy in some way or another.
*(Means something like "works the same, except for feature Z" where Z is sufficiently obscure)
I'm no lawyer, so I'd love to have a lawyer wade in on this. But seeing as you asked, I'll take a stab: such a contract could be perceived as being anti-competitive, and MSFT are super sensitive to being perceived to be anti-competitive. A product that is demonstrably less good can be sold for less. But to sell the identical product at two different price points to the same company, that sounds to me (as a consumer) unfair, and anti-competition law is intended ultimately to protect consumers. (aside: MSFT had a nice solution before Win7: keep selling XP under certain netbook restrictions because it is a different product to vista, and a product that is better for netbooks/ULCPCs (and a liked product). I'm guessing they wont have as much luck selling Vista on special netbook /ULCPC only terms once Win 7 is out.. )
http://www.winmatrix.com/forums/index.php?showtopic=23795 http://www.crn.com/software/212902058
(not the best sources, but they were the first hits. wsj reported it, too)
The answer to your second question is lack of competitive pressure. Windows isn't ideal for netbooks. When they came out first, Linux looked like it might win. But it didn't. They kept netbooks windows. They did this without a fight, without a netbook strategy.
At this point, there are no new competitors & no problematic trend. They now have a netbook strategy. Flawed or not, this is better then no strategy. Why should shareholders be worried.