Can Windows uefi stop Multiboot of Linux??

With the Windows 8 announcement there has been a lot of concern about comments made that Microsoft would require manufactures who want the "Optimized for Windows 8" sticker to use UEFI and key it to the MS installed OS.  So what would that mean?  Well the concern is that it would mean you couldn't install Linux.  It would also mean that you wouldn't be able to boot from any third party CD.  So no one, except maybe MS, would be able to create a bootable disk for repair, Antivirus, and disk partitioner will be able to create their disks or tools.   The there is the whole Monopoly issues.  Also the fact that MS has been spending all kinds of time and money to try and get the Open Source world off it's back and this would just destroy all of that work.  Then there is the whole issue with people who won't ever really install Linux but not buy the hardware just because they know they can't.  A Bios switch is a great way to have this particular piece of tech and use it.  After all Microsoft really does have a positive reason for wanting this done for antivirus protection.