I read about a new search engine called Spock at spock.com so I had a look and got a beta account.
The interface uses tagging, with some sort of machine learning/voting. So you can vote on tags people are given. The Spock robot sets tags too.
As well as tags, people get photos, some basic info - age, location etc and a short description, plus web sites and related people (both of which can be voted on).
It is an interesting way to classify people. It allows you to search on tags, so you can find all the Linux System Administrators easily.
One scary thingis that spock will import your contacts from various tools, email systems, outlook, and social networking sites, such as LinkedIn. In fact the system guessed I was the same person on LinkedIn. Clever, and scary.
So is it useful? Sort of. I haven't found a good use for it apart from searching for friends etc.
However I can see that the tagging idea may be useful in categorising people in systems where you want to track people's skills.