Reputation Systems: Online Communities
Trusting others online is not just important when money is at stake. The websites Hacker News and Reddit are designed to let users share news, websites, etc., with other users. The website StackOverflow is a Q&A site for programmers. Each of these sites is an online community that wants to promote good behavior and helpful posting about topics relevant to other users. To do this, they utilize reputation systems. Each user has a number that indicates her status. When other users think her posts, comments, or answers are worthwhile, they can upvote the post, giving her more points. On Reddit and StackOverflow, other users can also downvote these posts, taking away from her reputation. This type of system encourages good behavior because people want to maintain or improve their reputation. It also incites people to post new content that might improve their reputation. Deciding what type of reputation system to use strongly affects the character of the site and is an important decision in designing any online community.
Each site has a slightly different system. On Reddit, users accumulate "karma." Any user can give unlimited upvotes and downvotes. Karma is not actually displayed next to posts, so it is serves primarilty as a personal reminder about how your reputation is, not as an indicator to the community (although it is visible to people who click on your username). The votes also tell the website what posts are interesting enough to go on the front page of the site. On Hacker News, users can only upvote and not downvote at all. Besides this change, the system is relatively similar to Reddit's. StackOverflow is quite different. Users unlock achievements as they get more reputation. After certain reputation numbers, they can upvote, then downvote, then get various moderator privileges. Upvotes give 10 points to users. Downvotes take one away, but they also take two away from the downvoter, making downvotes a more serious commitment than on Reddit. Addtionally, your reputation score appears next to your name on your posts.
Each of these systems has a different effect on the content of the site and the character of the posts. For instance, because Reddit has unlimited upvotes and downvotes per user per day with no consequences of using them, people can downvote things just because they disagree with what the user is say or they think it's not funny. This encourages a more casual, opinionated, personal experience. The experience is appealing to many users, and the site has grown rapidly. Paul Graham, who founded Hacker News as a side project, explains "Reddit was a startup, not a side project; its goal was to grow as fast as possible." The karma scores next to the comments encourage people to try to post clever comments that will garner the laughter and upvotes of other users.
Hacker News
Hacker News, as evinced above by the comment above, does not allow downvoting at all. This method makes it impossible to downvote somebody you disagree with. The tone is more serious. Graham is still unsure if this choice will ultimately work to keep his site serious long-term. There is also no reputation score displayed next to individual comments. Pithiness does not get the same reward it does on Reddit. In a post about his experiences with the site, he says, "Hacker News is an experiment, and an experiment in a very young field. Sites of this type are only a few years old. Internet conversation generally is only a few decades old." He acknolweges the field is still developing and that sites like Reddit, StackOverflow, and Hacker News are making many guesses.
StackOverflow
StackOverflow, even more so than Hacker News, seeks to create a very serious, formal forum. Its FAQ page explains "StackOverflow is for professional and enthusiast programmers, people who write code because they love it. We feel the best StackOverflow questions have a bit of source code in them." The website explicitly closes all questions that are too general or not directly related to code. Downvotes are thus distributed sparingly. Users must feel very strongly that an answer is incorrect in order to downvote, since they themselves lose reputation by downvoting. Thus, users will not simply downvote an answer because they have a different opinion. Users' reputation points are displayed next to their questions and answers, encouraging good behavior even more so than the mere existance of these scores on Reddit and Hacker News. This upvote / downvote strategy, coupled with vigorous moderating by users, has so far been successful at keeping StackOverflow formal and on-topic.
These reputation systems are for motivating users to behave better based on the personal incentive of wanting to have a good reputation or to gain certain privileges on the site. They encourage users to promote or fit into the desired character of the site. Ultimately, as with any other site, the goal of these systems is to help the website be more trustworthy and more reputable.