Right now it is based on common interests and location. In the future it will likely look for other data that similar connections can be made on.
Airtime recently launched and they are following the same model as it turns out due to their close alignment with the Facebook community and the data it provides.
There are plenty of "meet new people" sites out there where you enter whatever you want about yourself. This is a different angle on that which provides functionality leveraging Facebook which Facebook itself is not going to provide.