Giles Crouch wrote recently about social search vs. general search, pointing out that people often search for information in their social network vs. in a general index such a Google or Yahoo! While we need to distinguish the cases when people search their social network for information about the network per se vs. information that the network refers to, there are circumstances when people make explicit decisions about where to search. It seems to me that there are several reasons why people may prefer not to use generic search in certain cases. In no particular order, these are:
Trust: People trust results that have been vetted in some way by people they know (or trust).
Context: A relationship between the searcher and some subset of his social network may be used to disambiguate common terms to produce more meaningful results.
Interaction: The big search engines are optimized for precision. When people are looking for open-ended information (i.e., engage in exploratory search), they may find it useful to interact with others to help them refine their information need and understand the question (or the path to the answer) better. One way to do that is to engage your social network. A recent CHI 2009 paper addresses this issue for people searching for information about crafts. Systems such as Twitter search also make it possible (although not guaranteed) to interact with people around the information they post. And of course explicit collaboration is a possible technique for finding information with other people.
So will “social search” be a Google-killer? No. Google and Yahoo are very well designed for certain kinds of precision-oriented searches. Will social search be as big a market as generic search? Probably not, for the same reason as above. Will it provide an useful complement to generic search? Undoubtedly. Perhaps a better question is whether Google will feel compelled to provide this functionality under its umbrella, and will do so by eating various smaller social fish.