After years of stagnating online white pages, a myriad of people search engines have emerged and Facebook joined the party last week by allowing its profile pages to be found. Never before was personal information so readily available. Looking for an ex, a long time friend or classmate? Checking out a potential hire? Planning a family reunion? Anyone owe you money? People search engines let you find information about other people from crawling, indexing, aggregating, consolidating and normalizing content from Web sites, social network affiliations, photos, blogs, news, public records and other user generated footprints. People search engines are also surfacing privacy issues, encouraging some to manage their online reputation like consumer brands should.

The social search space is growing broader, including submission and bookmark sharing, implicit and explicit voting, tagging and cloud navigation, commenting, and now an emerging “people search” category. Social search has become social networks’ underlying glue. Search is the Internet OS!

The people search space is getting crowded in a world where technology categories have often historically had just enough room for 2 leaders and a rotating third player. Mashable reviews about 40 social search engines and AltSearchReviews now maintains a Top 100 Alternative Search Engines list on a monthly basis.

Buzz monitoring picks up on noise long before Comscore’s panels can register statistically significant traffic levels. Online buzz is an interesting directional proxy for online sentiment and future success even though some started earlier and are better at generating buzz.

Wink Technologies is a People Search Engine that makes it easier to find people across the Web. Wink claims the largest index by providing search of over 200 Million profiles across social networks and on-line communities. Wink lets you add friends, monitor Web presence activity and includes a messaging platform taking it closer to some social networks. Wink recently expanded the sites it queries to include some people search sources, such as The Internet Movie Database and Wikipedia.

Ziki is a next generation search engine focused on people, powered by people. Ziki has developed its own algorithm to collect and organize information relative to a person. The platform also includes several community features such as networks, recent activity updates, similar profiles and views reporting.

Below is a video presenting ZabaSearch that I did not review.

People search engines face a number of challenges from directing comprehensive crawls, to de-duping content, extracting meaningful entities and even more fundamentally differentiating value propositions and building rational business models. What’s next? Are people search engines viable as standalone destinations or will they be rolled up as a feature by better integrated social networks. And general purpose search engines such as Google and Yahoo! will eventually better integrate people results leveraging their respective “OneBox” and other vertical intercepts. Critical success factors are actually very much in line with traditional algorithmic search: relevance, comprehensiveness, speed, ease of use and trust. The people search engine industry is still in its infancy and if Web 2.0 is about linking people, Web 3.0 could very well be about connecting and making semantic sense of people’s knowledge.

[PS: published from Google Docs, well done Google!]