16. The machine-readable medium of claim 13 , wherein the specific context indicates one or more characteristics that are shared by the plurality of second users.
16. The machine-readable medium of claim 13 , wherein the specific context indicates one or more characteristics that are shared by the plurality of second users. 17. The machine-readable medium of claim 16 , wherein the one or more characteristics include one or more of: websites visited by the plurality of second users, geographic information of the plurality of second users, demographic information of the plurality of second users, tagging history of the plurality of second users, search history of the plurality of second users, or social network history of the plurality of second users.