10. A computer system for detecting social networking spam, the system comprising: a computer-readable storage medium storing executable software modules, comprising: a selection module for: selecting a central member who is a user of a social networking environment; measuring degrees of association between the central member and other users of the social networking environment; and defining a social networking group containing the central member and other members, where the other members are a subset of the other users of the social networking environment selected responsive to the other users' degrees of association with the central member; an identification module for identifying that a new entry has been posted on a blog of the central member; an analysis module for: analyzing the new entry in comparison to a group usage profile for the social networking group, the group usage profile indicating a pattern of publishing activity of the members of the social networking group in posting information on blogs of other members of the social networking group over a period of time; responsive to the analysis in comparison to the group usage profile indicating that the new entry deviates from the pattern of publishing activity, analyzing the new entry using a global usage profile comprising a spam usage profile to determine whether the new entry matches a spam signature representing known spam; and a spam detection module for detecting that the new entry is spam, responsive to analyzing the new entry using the global usage profile; and a pattern module for determining a pattern of global publishing activity of users in posting information on blogs of other users in the social networking environment; wherein the global usage profile is based on the determined pattern of global publishing activity; and a processor configured to execute the software modules stored by the computer readable storage medium.
10. A computer system for detecting social networking spam, the system comprising: a computer-readable storage medium storing executable software modules, comprising: a selection module for: selecting a central member who is a user of a social networking environment; measuring degrees of association between the central member and other users of the social networking environment; and defining a social networking group containing the central member and other members, where the other members are a subset of the other users of the social networking environment selected responsive to the other users' degrees of association with the central member; an identification module for identifying that a new entry has been posted on a blog of the central member; an analysis module for: analyzing the new entry in comparison to a group usage profile for the social networking group, the group usage profile indicating a pattern of publishing activity of the members of the social networking group in posting information on blogs of other members of the social networking group over a period of time; responsive to the analysis in comparison to the group usage profile indicating that the new entry deviates from the pattern of publishing activity, analyzing the new entry using a global usage profile comprising a spam usage profile to determine whether the new entry matches a spam signature representing known spam; and a spam detection module for detecting that the new entry is spam, responsive to analyzing the new entry using the global usage profile; and a pattern module for determining a pattern of global publishing activity of users in posting information on blogs of other users in the social networking environment; wherein the global usage profile is based on the determined pattern of global publishing activity; and a processor configured to execute the software modules stored by the computer readable storage medium. 13. The system of claim 10 , further comprising: a validation module for validating that the new entry is spam responsive to determining that a user that posted the new entry was not logged in while posting the new entry.