Ubiquitous smartphones and always on access to umbrella social graphs are suddenly making these sort of tools possible.
And the opportunity is far larger than pick-up basketball, or even sports. Every school is a network, every employer is a network, every bar is a network, every office building is a network, every hobby is a network, every neighborhood is a network, and at an extreme level, every shared interest is a network, regardless of location.
All of these networks share two common characteristics. 1) They are not yet graphed in a mainstream way by Facebook, Twitter, LinkedIn, Jive, or any other dominant, online social service; and 2) They are all mappable with a smartphone.