Yeah, their algorithms are disturbingly good. They make
connections two and three levels removed from your OWN personal
experiences.
They're the equivalent of meeting the friend of someone you
barely knew, who knows someone from the same place you grew up
in, and it turns out you both sat next to each other in 4th
grade and didn't even know it.
If I remember right, the algorithm they use was come up with by
a girl undergrad student who had a revolutionary clustering
statistics system which actually seems to work. I don't remember
her name, and I could be wrong, but it's something I read about
a few years back.
Fascinating to realize our social worlds tend to be smaller than
we imagine them to be.