8. A computer-implemented method comprising: obtaining keywords from first user profiles of a first group of users of a social networking system who previously responded positively to an invitation; obtaining keywords from second user profiles of a second group of users of a social networking system who previously responded negatively to the invitation; determining an occurrence of a set of keywords in the first user profiles corresponding to the first group of users; determining an occurrence of the set of keywords in the second user profiles corresponding to the second group of users; selecting one or more of the keywords from the set of keywords based on a comparison of the occurrence of the keywords in the first group of user profiles versus the occurrence of the keyword in the second group of user profiles; and for a subject user of the social networking system not included in the first group of users or the second group of users, predicting a response to the invitation by the subject user based at least in part on whether the selected keywords occur in the user's user profile.
8. A computer-implemented method comprising: obtaining keywords from first user profiles of a first group of users of a social networking system who previously responded positively to an invitation; obtaining keywords from second user profiles of a second group of users of a social networking system who previously responded negatively to the invitation; determining an occurrence of a set of keywords in the first user profiles corresponding to the first group of users; determining an occurrence of the set of keywords in the second user profiles corresponding to the second group of users; selecting one or more of the keywords from the set of keywords based on a comparison of the occurrence of the keywords in the first group of user profiles versus the occurrence of the keyword in the second group of user profiles; and for a subject user of the social networking system not included in the first group of users or the second group of users, predicting a response to the invitation by the subject user based at least in part on whether the selected keywords occur in the user's user profile. 12. The method of claim 8 , wherein the keywords comprise words relate to declared interests of the users.