It's one of the fundamental aspects of Web 2.0 and is what makes modern websites so dynamic. The open nature of most "on-demand commentary" leaves it prone to abuse, however -- we're all familiar with ad and spambots filling up a forum with nonsense. Just how much web commentary is human-generated versus automated?
According to a recent study, real human interaction is apparently only a minor footnote in a sea of spam, malicious links and ads. A study by Websense earlier this year concluded that an overwhelming 95% of all user-generated comments are actually some form of ad -- or worse.
The Websense study focused on the world's most commonly visited sites, which largely consists of social networking and search sites. A little under half of those destinations provided some outlet for user-generated content, giving spammers more than enough room to roam.
It might be a problem for administrators, but how about users? On most forums (like ours), it's generally easy to discern an adbot from a real person. However, the more public a venue is, the harder it becomes to distinguish legitimate comments. Policing that sort of data on immensely popular sites like YouTube is surely overwhelming.