6. An apparatus 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 apparatus comprising: a user selector to access interaction data and contact data for the user of the first social networking site via an interface provided by the first social networking site; an interactivity monitor to determine an interactivity for the user based on the interaction data; a connectedness monitor to determine a connectedness for the user based on the contact data and to determine 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; and a network efficacy determiner to determine 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, the network efficacy determiner to transmit the first network efficacy to an advertising server to facilitate delivery of the advertisement from the advertising server to the user of the first social networking site.
6. An apparatus 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 apparatus comprising: a user selector to access interaction data and contact data for the user of the first social networking site via an interface provided by the first social networking site; an interactivity monitor to determine an interactivity for the user based on the interaction data; a connectedness monitor to determine a connectedness for the user based on the contact data and to determine 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; and a network efficacy determiner to determine 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, the network efficacy determiner to transmit the first network efficacy to an advertising server to facilitate delivery of the advertisement from the advertising server to the user of the first social networking site. 8. The apparatus as defined in claim 6 , wherein the connectedness monitor is to determine the connectedness based on a number of first-degree contacts of the user and based on a number of second-degree contacts of the user, and the connectedness monitor is to determine the connectedness by assigning a first weight to a first one of the first-degree contacts who has restricted a connection with the user and assigning a second weight to a second one of the first-degree contacts who has not restricted a connection with the user.