The Startup Revolution Starts With You is an interesting article that sort of reviews a new book -
Startup Communities - by VC Brad Feld. It talks about the importance of 3 key things in the creation of a startup community (which he defines as a geographic area like a city, not a coworking community):
1. Collisions - "those amazing, productive times when people who don't run in the same circles meet and connect".
2. Mobility - which greatly increases the number of collisions.
3. Density - meaning the more folks there are, the more likely they are to have collisions.
These are new/different terms for things that have been often pointed out in the past. Collisions are, of course, a lot like the way serendipity is used in the coworking world. And all of these are based on weak tie connections.
This book and article are another example of the growing number of sources talking about the importance of place.
The New Geography of Jobs is another example, and well worth reading.
This is just an FYI because I think these sources provide good information on why coworking communities are good for business:).