Valdis Krebs points to some more research that confirms the Allen Curve works (proximity creates opportunities for serendipitous interaction): Those close by, form a Tie. The article citation is Desperately Seeking Spillovers?: Increasing Returns, Industrial Organization and the Location of New Entrants in Geographic and Technological Space by Aharonson, Baum and Feldman.
I couldn't find a good, descriptive excerpt, so I'll go with this funny one:
"Eventually [technologists] are all going to meet in the nearby coffee shop. The basis of agglomerations and the benefit for high tech firms is the flow of knowledge," Aharonson said.
So, all that coffee I drink in coffee shops is a good idea! Now I just need to find a good, local coffee shop along the Rt 128 corridor.