If Web 1.0 was about linking information then Web 2.0 is really about linking people as pointed out by Mills Davis from Project10. The social network phenomenon is creating an unprecedented and growing amount of buzz and is already channeling significant amounts of traffic around. IceRocket Blog Trends reports about 400 posts a day referring to the phrase “social network“. Nielsen BuzzMetrics Blogpulse shows an increase of 200% in 6 months from 0.015% blog share of voice in March 2007 to over 0.045% in September 2007.

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.

Spock claims to be the online leader in personal search, helping users find and discover people with over 100 million people already indexed. In addition to scouring social networks, Spock does a nice job at differentiating its feature set by letting users vote. And the Spock Power score determines how much influence you have each time you vote or add a tag, image, link, or relationship. Complimentary tour below.

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.

PeekYou has been in stealth mode since October 2006 and officially launched in beta this past July. PeekYou’s differentiation claims revolve around i) de-duping numerous identities into one consolidated snapshot profile and ii) platform openness.

ZoomInfo contains profiles on more than 36 million people, including biography, employment history, Web references and other Web links such as blogs. Founded in 2001, ZoomInfo is a “relative” industry veteran, more focused on the business world, closer to LinkedIn-type content. The company also gives access to executive profiles requiring a paid subscription.

pipl positions itself as The most comprehensive people search on the web. pipl aggregates more than social networks, also including public record information from PeopleData such as addresses, birthdays, passenger records from ellisislandrecord and more. Unlike a typical search-engine, Pipl is designed to retrieve information from the deep, sometimes referred to as “invisible” Web, estimated at 500 times that of the surface Web.

Ex.plode.us is an easy way to find friends and those with common interests, no matter what social network or service they use. You can search for names or interests. Not unlike other engines, the company’s vision is to build an application that acts like the glue between social networks, breaking down silos and opening up the web using open standards. In addition to crawling and aggregating social networks, ex.plode.us lets you add friends and comments on friends’ profiles.
Rapleaf, founded in 2006, is positioning itself a bit differently. Use Rapleaf to build, promote, and manage your online reputation. Rapleaf’s application is a twist on eBay’s seller ratings and emerging B2B brand monitoring plays like Andiamo Systems, Converseon and BuzzLogics. The Rapleaf score is calculated using data from ratings given about a person and other online information such as social networks. Members can also export their reputation score widget to blogs and other networks. As pointed out by Stefanie Olsen from Cnet, Rapleaf has no visible link to TrustFuse, but TrustFuse’s privacy policy mentions that the company is a wholly owned subsidiary of TrustFuse. And TrustFuse sells data to marketers so they can better target customers.

Naymz, not unlike Rapleaf, is positioning itself as the place to maximize your business and job opportunities by promoting your good name and reputation. A little like LinkedIN, Naymz has developed a confidence level index. This reputation index is calculated from a number of variables, including profile completeness. Naymz goes one step further and lets users subscribe to someone else’s recent Web activity such as blog posts and profile updates.

WikiYou, “A Wikipedia for people” according to TechCrunch, is the unauthorized biography of every person on earth. WikiYou also aggregates friends and let’s you discuss, comment on someones profile and add videos.
As for traffic, the space is in its infancy and the jury still out. ZoomInfo is way ahead with about 1.3 million unique visitors a month. Most everybody else remains below 100K visitors according to Compete and QuantCast. This said, all are significantly increasing usage traction and visitors are giving them a trial, generating around 5 pages per visit.

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!]