Limitation. The OS will not automagically allow it. Because what could *ANYONE* need that for!
rEFIt hasn't been properly updated for the 5,1 Minis yet. Sure it'll work, maybe. After 4 reboots... maybe.
And yes, I'm very interested in getting Linux on the Mini.
I just haven't had the time or inclination to futz with it until the PCI compliance gawds are dealt with.