I made a curious observation today that the psychological concept of personality may be useful in characterizing social websites. For example, a website can be introvertive or extravertive. As in psychology, these are not absolute categories, but rather an indication of a bias toward one end or the other.
An intravertive social website draws attention of its users towards its local content, while extravertive social website draws attention of its users outside towards the content present on other sites of the web. Two examples to illustrate these are 3form and StumbleUpon, respectively. Both implement essentially the same technique, human-based evolutionary computation. This technique allows people to contribute items to the database, draw random samples from the population of items, evaluate sampled items. The software computes a fitness function from those evaluations and uses it in later sampling. However, 3form and SU use this technique in remarkably different ways. 3form samples content of its own database, provides an easy way to socially bookmark/evaluate/comment on it. However, it is less easy to bookmark any external resource or comment on it: you have to cut and paste its link into the web form and not many people bother to do it. This makes 3form community rather introspective and focused on the content found locally rather than resources found elsewhere. StumbleUpon, on the opposite, samples from the database containing primarily external resources found elsewhere. It naturally directs user attention to perceive the world outside of SU. SU makes it very easy to bookmark and evaluate any external resource with a single click. It is not true, however, for the local resources found at SU’s own site. When I start using SU I initially thought that, unlike most blogs, SU ones don’t support commenting. Then I found that it is possible to comment on a post, but not as easy or intuitive as commenting on external resources. You first need to find a permalink to the post you want to comment on (shown as the date of the post), click on it to open the post in a single window, then you can use normal SU buttons to evaluate and comment on it. Not many people take effort to go this way, so most posts at SU blogs remain without comments.
Though it might be a pure coincidence, but nevertheless interesting that the personality of a website reflects in this case the personality of its architect. My MBTI profile is INTJ (introvertive) and StumbleUpon chief architect and CEO Garrett Camp is ENTP (extravertive).
What about other websites?
Wikipedia was always mildly introvertive. It was always easier to link to an internal page than to create an external link. In addition, Wikipedia culture is discouraging creation of external links. Recently, Wikipedia has become more clearly introvertive by making you solve CAPTCHA, when you try to contribute a link to an external resource or even fix a broken link. This, undoubtedly will decrease the amount of external references in Wikipedia.
Del.icio.us and most social bookmarking tools are extravertive, their primary purpose is to direct attention to the other sites. I am quite curious if their creators are extraverts as well.
Digg seems to be pretty balanced in this respect, it requires high effort from any user trying to use it because of many CAPTCHAS, but commenting on an internal post and submitting a new story with an external reference involves about the same amount of effort.