I don't thing MS is worried at all about numbers of Macs sold. In fact, it might even be good for MS. A very large number of those Macs are going to buy a Windows. The difference is that they are going to buy that license directly from MS as a download or from a retailer at full retail price. MS either gets the entire markup, or shares the full markup with the retailer. My understanding is that an OEM's Windows license, that come with PC hardware, has been bought by the OEM at a huge discount. MS doesn't get much more than a few dollars licence, and counts on the huge volumes to make their money. I'm guessing that the Windows licenses MS sells to that 12% marketshare of Macs more than makes up for the licenses they would have sold to the OEMs otherwise.
Same thing for Office. A hefty portion of those Macs are buying Office licenses at full retail price. In this case they are also buying discounted licenses through school and work, but they would have access to that pricing regardless of the platform. What the Mac owners are not getting are the heavily discounted OEM Office pricing deals. So again, I would argue, MS is probably making more money off the Office sales to those Macs than they would have otherwise.
Where MS needs to be worried is in the tablet market. At the moment they don't have much of anything (if anything at all, yet) to sell that runs on iOS. Every tablet Apple sells is, in this case, a totally lost sale for MS. I think we will see a huge push for the Surface in the next while. MS has to reclaim some of its total marketshare that it is losing to the tablets. At the moment, my feeling is that MS is totally irrelevant in the tablet market - and it has to become a player, or else it will suffer hugely.
