My wife’s sister's kid made coin box out of their Denon home theater receiver putting coins through ventilation grill during several months. The family realized that only after they saw a smoke coming from the unit one day.
Should we care if a piece of equipment comes from a pet-free, kid-free, smoke-free home?
I agree that I do not want a preamp or speaker coated with a film of smoke, but I am confused as to what a child or pet could do that would not be otherwise visible. You would see the cat scratches on the speaker grill, the dog chew marks on the rack, the iguana turds in the amplifier cooling vents. And what's a little dog hair among friends? As a 3 year old, I supposedly put my finger through my grandfather's new DIY speaker but I'm pretty sure he replaced the drivers so even that doesn't really matter. Most things will be visible and/or easily remedied. Maybe the price will even be a little lower because of the cosmetics. If it doesn't mess with function, not a big deal to me.
What concerns me more is does it come from a drunk-free, drug-free home. I think befuddled owners are far more worrisome than pets or children.