Then why is Reddit one of the most popular sites in the US?
What defines Reddit is it's ranking algorithm, it's tree-shaped threads, and it's subreddits.
Which are not akin to subforums. Biggest difference being that anybody can very easily create a subreddit and moderate it.
Tree like threads existed on forums long before reddit. But this is one of the reasons I'd say reddit is more like a mailing list or a newsgroup.
> and it's subreddits.
Again, like a mailing list.
> What defines Reddit is it's ranking algorithm
This is it's big difference, I'm still not convinced ranking algorithms do more good than harm though.
I never said that reddit invented any of those things.