My first question would be when it comes to validating your copy of an OEM on a self built PC how do they know if the PC is self build or purchased? They don't ask any pertinent questions, they just validate it.. If indeed it's a hard and fast rule concerning the use of the OEM why is there no effort made to determine who it is asking for validation?
As pointed out in the article you linked to, even using the M$ search engine he couldn't even find a retail version of the operating system he was looking for, only OEM versions. And the detailed information on the use was nowhere to be found. The average Joe will buy the OEM. I did. Knowing that it couldn't be used on another PC if/when that PC died.
Is this now just a hook M$ can/may/will use to declare your OEM copy invalid somewhere down the road and require you to purchase another license if you wish to continue using it? Or a way to force you to upgrade?
The whole thing sound devious and underhanded to me. I think this will just encourage more people to use cracked copies of the operating system they want.