Although there are rumors that the reason for their stringent requirement are graphics based, the official reason is still unknown.
So which macs will run OS X Mountain Lion (OS 10.8) and which ones will remain fettered to OS X Lion ?
- iMac (Mid-2007 or later)
- Macbook (13-Inch 2008 or later / Aluminium)
- Macbook Pro (13, 15-inch Mid 2009 or later, 2.4 / 2.2 GHz / 17-inch, Late 2007 or later)
- Macbook Air (Late 2008 or later)
- Mac Mini (Early 2009 or later)
- Mac Pro (Early 2008 or later)
- XServe (Early 2009)
(list from Tuaw.com)
If your Mac isn't on the above list, then it probably won't work with Mountain Lion.