Some of the PersonalTelco folks (especially myself and DonPark) have been wanting something along these lines for a while. Partly it's a way of getting cheap office space, partly a desire for community and partly a hope for increased creativity and fun when surround by other people.
I found this article on Margin Walker. It's pretty interesting.
Other sites:
JamesSteven's and others Deck Space in GreenwichEngland.
Affinity Lab
Digram showing relationship between 1/2/3/4th places (source nobilid.com).
See also: ThirdPlace