So I'm wondering, what sort of problem could happen if the microprocessor is run 'too fast'? Would that shorten the lifespan of the chip? Or does runing it out of spec lead to logic errors or something like that?
Essentially, what is the risk of running the arduino too fast?
Many individual and a few commercial offering run their board at 3.3vdc at 16Mhz and report no problems. The risk of running outside the AVR datasheet recommendations is random logic errors, not any shortening of device life. So It's not something that AVR recommends, but again many report no problems with 'overclocking' the device, so you pays your dime and you take your chances. I wouldn't recommend doing it if the board is controlling a nuclear reactor or a cat-scanner, but if your just blinking leds, or making sound effects no problem.
Speaking of cat-scans, did you hear this one?
A man is concerned about his dog so he takes it in to the vet for a check. He places the dog on the examination table and the vet looks the dog over. After a few mins the vet tells the man "I think your dog is dead". "Dead!" says the man, "are you sure, I would really like a second opinion". Ok says the vet and he goes to a door and opens it and in walks a cat. The cat jumps up on the table, takes a few sniffs at the dog and then jumps down and leaves. Yep, your dog is dead, that will be $580 please. "$580! for just this little time?" asks the man. "Well I only charge $80" says the vet, "but the cat-scan runs you $500".
Lefty