How do you think of Reddit in that framework? Reddit itself is explicitly a tool for creating, basically, community sites. How closely does it fit with your vision of a tool for crafting social networks? When do you predict it will fail?
> Sure, reddit has a community aspect, but it's really just a side dish compared to the content (links).
Maybe if you stick to the default subreddits that are composed entirely of memes.
The main reason that I use Reddit is for the discussion; I highly, highly doubt that you're going to find /r/askscience-calibre conversations on Facebook.
OTOH, subreddits like IAMA, AskScience and ELI5 are fairly significant parts of reddit. In fact, most of the top items in /all are memes that refer back to things that happen within Reddit, so I'm not sure the links to external websites are nearly as important as the community these days.