At first they don't notice you, then they laugh at you, then they fight with you. And then you win. Mahatma Gandhi

Fears that Microsoft will affect UEFI (an interface designed to replace the BIOS), especially with a feature like Secure Boot, come true to achieve their goals.

The recommendation from Microsoft to manufacturers of ARM devices requires that the ability to disable Secure Boot in UEFI is not possible.

Prehistory
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At the end of last year, Microsoft announced that Windows 8 would require a “secure boot” to boot. UEFI has been working on this feature for several years. It works as follows, UEFI stores the “secret keys” in the operating system. These keys are used to access UEFI for everything that it wants to boot, for example, operating systems. If the corresponding key is not registered in the operating system, it will not be allowed to boot.

The Linux community is interesting to explain to manufacturers of ARM devices that transferring “keys” to Linux will be very difficult to implement, which makes it almost impossible to install Linux on Windows 8-sharpened devices.

Microsoft tried to reassure the press, explaining its position , Canonical also expressed its opinion on this issue.
Microsoft said it would not require hardware manufacturers to prevent the Secure Boot from shutting down. But now it seems that this advice applies only to traditional PCs, and not to ARM devices.

"Disabling Secure Boot should not be on ARM systems"

Microsoft's official guide for manufacturers wanting to get Windows 8 certified for their devices.

On page 116 of this manual there is paragraph number 21, describing how and when support for enabling / disabling Secure Boot should be enabled:

MANDATORY REQUIREMENT: Enable / Disable Secure Boot.

On non-ARM systems, you must realize the ability to disable Secure Boot through the firmware installation interface. A physically present user should be able to disable Secure Boot through the installation interface without owning Pkpriv (the note seems to be the name of the OS boot key in MS). Software shutdown of Secure Boot should not be possible either during the boot process or after the end of the boot process using EFI.

Subtotal

Microsoft is moving to combat the Linux family. Let's be realistic until the moment when Linux will take a serious share of the PC market for a long time to wait, but such steps by the MS testify that Redmond began to recognize Linux-based operating systems as competitors.
You can stock up popcorn will be interesting, like any competition. And she often promises benefits to customers.