Stackoverflow. Its closest competitor, experts exchange, was a slow website that required you sign up to see an answer that was rarely useful. There's a direct correlation to SO and dollars of revenue I've driven.
Experts Exchange also used to do that awful thing where they let Google index the solution but would hide it from visitors until they'd signed in.
I believe Google penalised them for doing it so they used another sneaky trick where they showed a obscured/pixelated answer first and then the actual one further down than most people would scroll.
What's wrong with www.ExpertSexChange.com? People deserve to hire experts for that don't they? /s
Somewhere out there must be an RFC that discusses the original thought process behind designing for case sensitive vs case insensitive domain names, or why domains should be case insensitive while URL paths should be case sensitive... Ironically this SO post seems to be a decent starting point for my curiosity: https://stackoverflow.com/questions/7996919/should-url-be-ca...
I wouldn't give them 10x, but certainly 2-3x for junior developers compared to predecessors and 1.2x for others. Which is still incredibly significant and nothing to sneeze at.
Stack Overflow is much better than Quora. Quora has gone downhill over the last few years with paid contributions and modal nags. It sea they will also sign me in after I click a link in their email digests. I don't know how that can be secure