You can start local, but don't limit your network to your lab, department, and university. (sciencemag.org)
By limiting the network to people living within a stone's throw of you, worrying if they live in another state or even country is long gone! (wisconsinflirt.com)
Most members limit who can see details of their lives, and except for the obsessive «friend» collectors among us, most limit their networks largely to people they actually know. (epolitics.com)