Come to think of it Hubski has badges too, but they're purely social. I don't know if they're actually motivating users to post more insightful content, but I think they're undeniably a good feedback mechanism to show one's contributions are appreciated.

Reddit has plenty of ludic aspects as well. In fact, Reddit is probably one of the better examples of how gamification should work. Many users are quick to point out that the voting system, coupled with a user base rabid to use it, creates a Skinner box. Skinner box's are most effective when the payout is set to 50%. Subjects naturally get giant spikes of dopamine when they honestly don't know whether they'll win or lose, and when posting to Reddit most people seem to have no idea if their post will be met with adulation or derision.

That's only one mechanic though, and that's where I feel most people would stop and think, "Well, we just need some kind of operant conditioning mechanism to hook users." That is probably a good place to start, but the truth is the community of Reddit happens to create something more worthwhile. It creates spontaneous cooperation and competition. For instance, "Let's all band together and try to set up this rally," or "Let's all take different sides to this controversial issue and discuss it." This is a more pure aspect to play that strikes closer to the things that motivate real people and not laboratory subjects. The fact that Reddit does have achievements but no one pays attention to them anymore is exemplary of this.

I think there's also a very negative aspect of this that doesn't get talked about. Which is these games can also create very motivated destruction. Instead it becomes, "Let's all band together and send death threats to this person we suddenly hate," and "Let's split into Feminists and MRAs and spend 6 years just shouting at each other." When we finally get a better grip on how to use these ideas to tap more energy from people, we also need to be able to focus that energy towards meaningful endeavors.