Yeah... I registered mine online the day I got it.
Too bad you can't find out if the original owner registered it.

As mentioned, you'll most likely not ever need the warranty, but who knows?
Even if they don't cover 2nd owners with warranty work (sending it in for repair), would they possibly send replacement PARTS at no charge? Other companies do.
(I'm new to S&W ownership, so I'm not sure about their replacement parts policy)