Sparknotes spawned a quiz site, TheSpark, that eventually morphed into OKCupid... that started out being successful because it gamified making quizzes for people, and then stumbled on the miracle of asymmetrical matching. Ie. matching people not based on common interests per se, but on curiosity... or "satisfying" their curiosity. Turned out to be a great way to get to know yourself, and what you are really looking for... I'm sure a lot of people figured out what to look for in their true ideal partners, and some even managed to meet them on the site... Match.com takeover obviously completely ruined everything... rooting for more copies, hell, even a decentralized protocol, that can bring back notjust the romantic, but also the platonic- and self-insight-giving parts of TheSpark...