It's the "like likes like" in a paper about networks. I like it
   smile emoticon There's stuff a few years about about properties
   of spun glass and a marvelous paper about networking and
   "nearest neighbor" clustering a few years back that this reminds
   me of. Also reminds me of how coffee grounds sticking together
   during a space mission was accidental confirmation of one of the
   theories of "How did the first particles of planets start
   sticking together when gravitational attractors were too weak" -
   and the answer was static electricity basically. If you zoom out
   away from the details of many of the forces and fictional forces
   in physics, you'll see they more-or-less follow these same types
   of patterns.