The history is often overlooked: when digg imploded/shot itself in the foot, Reddit was in the right place at the right time and got lucky. Somewhere for the exodus to go to. Reddit itself was failing fast and on its last legs at the time held afloat by its core users and that's it. They didn't know what they were going to do and rather than being visionaries in any way really they got lucky hosting everyone with a slew of very standard web 2.0 features. And as with any social site, it's the userbase/community that pulls it thru darkness to the where it is now.