1. A method to determine a first network efficacy of a first social networking site to facilitate delivery of an advertisement to a user of the first social networking site, the method comprising: accessing, by executing an instruction with a processor, interaction data and contact data for the user of the first social networking site via an interface provided by the first social networking site; determining, by executing an instruction with the processor, a connectedness for the user based on the contact data; determining, by executing an instruction with the processor, an interactivity for the user based on the interaction data; determining, by executing an instruction with the processor, a network constancy for the user by determining a ratio of (a) connections between contacts of the user of the first social networking site to (b) at least one of: (1) broken connections between the contacts of the user in response to removal of the user from the first social networking site; or (2) connections between the contacts of the user that exhibit changed degrees of connection in response to removal of the user from the first social networking site; determining, by executing an instruction with the processor, the first network efficacy of the first social networking site based on the connectedness, the interactivity, and the network constancy, the network constancy being based on the ratio; and transmitting the first network efficacy from the processor to an advertising server to facilitate delivery of the advertisement from the advertising server to the user of the first social networking site.