1. A method for proximity determination, comprising: receiving one or more network identifiers, each associated with a corresponding network, from a first mobile device; receiving one or more network identifiers, each associated with a corresponding network, from a second mobile device; processing the network identifiers received from the first and second mobile devices to determine whether the first mobile device and the second mobile device are in proximity to one another; receiving a network identifier from a third mobile device, the network identifier received from the third mobile device being different than the one or more network identifiers received from the first mobile device; comparing the network identifier received from the third mobile device to the one or more network identifiers received from the first and second mobile devices; and determining that the first and third mobile devices are in proximity to one another when it is determined that: at least one of the one or more network identifiers received from the first mobile device matches at least one of the one or more network identifiers received from the second mobile device; and at least one of the one or more network identifiers received from the second mobile device matches the network identifier received from the third mobile device; accessing a statistical sampling of network identifiers received from a plurality of mobile devices; determining, based on a comparison of the network identifiers received from the plurality of mobile devices, which of the plurality of mobile devices are in proximity to one another; and generating a tree structure based on determined relationships of the plurality of network identifiers.