What do you think about Reddit? Topics are enforced and have an API.
I've seen this affect sites like Stack Overflow as well. At the bottom of any popular question are usually very low-effort answers from posters who really shouldn't have answered at all. I wonder if it's an example of their otherwise well-executed reputation system creating noise that might have been avoided.
There's a blog, book, and wiki.
Some keyword searches: http://www.worldcat.org/search?q=kw%3A+online+reputation+sys...
https://scholar.google.com/scholar?q=online%20reputation%20s...
You can't have "democracy" and "voting" and "algorithms" and then have high content.
Subreddits, users, posts, searches, and a number of other elements.