not required. I think it's a question of what type of customer service you want to offer. A seller is not obligated to replace lost chips, but it sure is good business if you want repeat customers.

If an item is expensive or cannot be replaced, then the seller can decide if he wants to invest a couple of bucks in keeping a customer happy.

I compare it to shopping in a store. Do you like to see signs that say "If you break it, you bought it"?