What traits specific to Reddit as opposed to a hypothetical generic alternative forum platform do you think are major contributors to those social trends?
It would surprise me if the winner in that space didn't have a public voting mechanism. Digg, Reddit's early major competitor had one, and heavy-handed moderation surrounding the HD-DVD decryption key leak was one of the major inflection points that drove users from Digg to Reddit. Stricter moderation during that time period would have been a losing strategy.