My initial skepticism was based on the premise that "people search is a feature, not a company". The general problem Spock is solving is known as "entity search", and is not rocket science. This isn't meant to criticize Spock, but simply to point out that there is no algorithmic moat (or intellectual "secret sauce") that could stop a big competitor from building a superior service.
In fact, it appears that Spock may have given up on that goal. It seems that their approach for entity search is now significantly different from what Tim talked about at Web2Expo.
When I signed up, I was asked to supply usernames and passwords for every one of a range of existing services. Hotmail, GMail, LinkedIn, MySpace, Facebook, Yahoo, and more. In fact, it would not let me register until I had supplied a username/password for at least one other service!
In other words, if you want to be found on Spock, you have to already be discoverable on some other service. The Spock search results look like an aggregate of listings from MySpace, Wikipedia, LinkedIn, and anywhere else that someone gave up a password.
So it appears that Spock is now attempting to be a portal that aggregates and syndicates all of the other social networks, rather than an people search "engine". I don't have a problem with the idea -- in fact, most of the "entity search" players in the market long ago realized that sites with topical user-generated content (like Wikipedia or Facebook) are essentially entity databases. It's the way they're going about it that gives me doubts.
First, for many people, the MySpace or Facebook profile is their most prized online possession. How many of them will want to give full control of that possession to a company they never heard of, and what value do they get from it? And for people like me, who already appear at the top of the Google search listings, what incentive is there to enter all of my information into a walled garden like Spock? Anything that I want people to find about me in a search engine, they can already find. And the features they offer are all available on other social networks. I am skeptical about an attempt to birck over a user experience that aggregates across other social networks. Spock doesn't solve any problems that I have.
I think that entity search is a great idea, and the big search engines will add features related to people search. But I don't think they'll do it this way. Who knows, maybe the "ask people for all their passwords" and "brick over LinkedIn/Facebook" approach will work out. But not for me, not for now.