Reddit is a service that has truly created a community. And a community isn't just the good, it is the bad. For every bus driver being tormented that is saved with kickstarter story, you can find one where a user is being pestered and encouraged to commit suicide by trolls, or things like the Boston Marathon manhunt.
I feel as if the Reddit community is hitting a point of critical mass where one of two things are going to happen:
1. It becomes much more segmented, with specific subreddits disregarding interaction between users who generally stick to a few specific few, and these communities do well because they are now the size of what used to be entire large chunks of Reddit.
2. Reddit will fail to deliver enough new features fast enough to justify the spending, and it will result in many feeling slighted and we could see a digg-esque migration of users to some other service X that pops up.
Personally I have stopped using reddit as much as I used to, because I generally only peruse the programming and ruby/rails and clojure sections. Most of the stories I see posted are already on HN and have better discussion here. However, I am obviously a very specific case and the reddit userbase is quite widespread now that it has gotten so popular.
It really will be interesting to watch.