Business2.com:

“Social networks are a dime a dozen these days, but last week a new one launched called Geni that is actually quite different than anything else out there. David Sacks, Founder, thinks of Geni as more of a family network site than a MySpace-style social network.  As he puts it:

You have social networks and professional networks.  The glaring ommisison is there is no family network. People will want important networks for all different parts of their lives and they will want to keep these networks separate.

Geni is a private family network where only the people you invite can see your profile, or the profiles of your other family members.  But what makes it unique (and addictive) is that it is first and foremost a simple Webtop application that helps you and your family collaboratively build your family tree.  The first thing you see when you go to the site is a box inviting you to put in your name and e-mail address.  Then arrows pop up allowing you to add other boxes for your parents, spouse, children, siblings, etc.  Every time you add someone’s e-mail address to their little box, they get an invitation to join your private family network on Geni and help you build out the tree.  One of Geni’s long-term aspirations is to build a family tree of the whole world.”