That users used KMS activation after activating fully with Media Center key and invalidate the activation?
As has already been stated there are so many legitimate KMS activation's that it would be impossible for MS to determine who is and who is not You must be able in to add WMC to VL editions of Win 8 otherwise the keys would not work on KMS activated machines Personally I cant see there being any comeback on this what so ever
MS could do many things in this direction but the main question is if they want and if the big bucks are to be found in this way of pursuing. The many many ways of circonventing legal activation are meant for beeing nice to companies which bring the real big bucks. The private consumer usage is for spreading Windows like cancer and that's more valuable for MS as tourchering every pirate for 200 bucks. Now with Windows 8 there is the possible cash cow of the Windows Store. That there are dummy seemingly unhackable ways of licencing Windows is only to quieten the copyright lawers which belive that if they don't seemingly trie to cirumvent pirated copies so they lose all possibilities of charging for there products. Yes this sounds crazy but that's reality of the crazy law in the US of copyright I think if the Windows Store will become a fools way of making money for MS then they will drop the price to a symbolic penny or make Windows even free for consumers for a non comercial usage in the next version of Windows. Less (legal) cost of Windows = more copies of Windows installed = more market for the Windows Store = more sells in the Windows Store.
As far as I know, I was the one who originally investigated this, and I came to the conclusion that no; currently, and in future, it would be difficult if not impossible to prove beyond a shadow of a doubt that someone had used KMS activation and then applied the ProWMC key. However, there IS residual key insertion and activation information retained in data.dat; the question is, whether or not Microsoft have a way of actually decrypting the contents of the file, or whether or not it's designed to be double-blind to prevent exploits from using it to bypass activation. The bigger question is, do they care? As I've said time and time again over the years, in my experience working for them in the past, Microsoft do not care about home users running pirated copies of Windows. 95% of their revenue comes from OEMs, Volume Licensing, Software Assurance, and TechNet/MSDN subscriptions (and now DreamSpark). Retail sales are quite literally a drop in the pond, and are only there to provide a means of obtaining Windows for those people who are just "built" to do things by-the-book.