As long as you are not buying/using a garbage PSU, then you should be OK. A good PSU will have built in short protection and shut down (without damage) if something is shorted.
Most motherboard shorts I have run across have been from blown rectifiers/mosfets etc. and even then they are more likely to go "open" vs "short". I have run across other components like hard drives and optical drives that shorted out as well. Sometimes you can get lucky and see charred components, sometimes not.
If you want to do a postmortem on the current fried PSU, first look at the components (vregs and mosfets) attached to the internal heatsinks. You can often see a scorch mark, or sometimes a chunk blown out of the component as well. Be careful poking around in a PSU as those big caps tend to hold a charge for awhile and can zap you.
Edited by dpunisher, 19 December 2008 - 04:03 AM.
I am a retired Ford tech. Next to Fords, any computer is a piece of cake. (The cake, its not a lie)
3770K @4.5, Corsair H100, GTX780, 16gig Samsung, Obsidian 700 (yes there is a 700)