Benchmade doesn't ask for a receipt or proof of purchase, and warrantied the crooked river I bought for cheap on the bay with an oversharpened blade and cracked handle. No questions, they replaced the blade, handles, gave me a deep carry clip... They made a customer for life with that service. Buck will warranty any knife as well I believe. I haven't had to use it but I've seen the service they give here on the forums. It's exceptional. I think when most companies say they only warranty to the original purchaser, it's something they have to do for legal reasons. I know Kershaw/ZT say they need a proof of purchase but never enforce it. Same with Benchmade. If a company selling $2k knives actively looks for secondary market knives to deny warranty, that's going to lose them a lot of business.