Social search ... incorporates both automated software as well as human judgments ... That's what makes social search intriguing -- and fundamentally flawed ...On this last point, the mainstream and the profits of the targeting that broad audience attract spam. If sites using tagging and other forms of community-generated content enter the mainstream, they will be flooded with spam.
No matter how many people get involved with bookmarking, tagging, [or] voting ... the scale and scope of the web means that most content will be unheralded by social search efforts ... People-mediated search will never be as comprehensive as algorithmic search.
Another problem arises with tagging ... Tags are not a panacea for categorizing and organizing the web ... Without [a] controlled vocabulary, tagging ultimately remains a chaotic, messy process.
Another factor is human laziness ... We've always had the ability to add tags and other metadata to our Microsoft office documents, and yet how many people do this?
We also have a problem with idiots and spammers. Some people ... do a poor job of labeling content. Others will deliberately mislabel content ... In both cases, it's difficult ... to recognize this spuriously labeled content ... it's difficult to filter the noise from the signal.
When that happens, the problem will be how to automatically filter all the tag and user-content spam, a problem that looks little different than automatically filtering web spam.
See also the article Chris posted a day later, "Who's Who in Social Search".
See also my previous posts, "Yahoo gets social with MyWeb" and "Different visions of the future of search".