Naturally as operating systems advance, older computer models will slowly stop being able to support them due to their hardware not being sufficient enough. Such was the case with OS X Leopard back in 2007 where Macs with processors slower than 867MHz were not supported, and it was repeated again with Snow Leopard where support for all PowerPC Macs were dropped. Well if you liked what you saw with Apple's upcoming OS X Mountain Lion, and if you have not changed your Mac computer in the past 2-3 years, you could be out of luck if you were hoping to upgrade.
Ubergizmo, OS X Mountain Lion dropping support for older Intel-based Macs
