> Personally I think it is an excuse to get people to upgrade. I see absolutely nothing that would require a crazy new video card. (I've been running ML for months)

The 32-bit Kernel no longer exists/is no longer maintained/was not upgraded for Mountain Lion.

The unsupported models have video cards that do not have 64-bit graphics drivers available for them.

The 64-bit Mountain Lion kernel is incapable of loading the old 32-bit graphics drivers for these cards.

Thus these video cards are literally incapable of supporting Mountain Lion.

>Personally I think it is an excuse to get people to upgrade.

Well of course it is, they're a hardware company. I don't think there's some conspiracy to deprecate 6 years old computers when the shelf life of a computer in the industry is 1-3 years - in other words, I don't think they're being unreasonable.

I think they're just standardising on hardware that is capable of OpenGL 3.0 and above. Most of the older Macs that don't support ML are the ones with Intel chips that only support 2.1 if I remember correctly.