Yeah i agree, someone should take lessons on how to look after their stuff, expensive PS3's not being looked after puzzles me to say the least.
On the other hand, i don't see what the deal is with Sony not fixing it, thats like buying a PC from PC world and then taking it back and saying sorry its full of dust were not fixing that under warranty. How can you help prevent it?
Fair enough, the outside of the case should have had a clean, but the insides would be no better for it, if the outer case is a risk to health, then i'm sure as hell the insides are aswell, in which case this probably applies to every other PS3 thats sent in for repair.
I'm getting my PS3 this christmas from my fiancee, while i consider myself to take good care of my gear, i hope i don't run into any problems like this in the event it breaks down.