11. A system comprising: one or more hardware processors; and a memory coupled to the processors comprising instructions executable by the processors, the processors being operable when executing the instructions to: receive an indication of a first user action by a first user; and when the indication is received: analyze content of the first user action; determine a topic of the first user action based at least in part on the analysis; determine whether the tropic is trending; determine whether the first user has indicated a preference to exclude posts associated with the topic or a category associated with the topic; and in response to a determining that the topic is trending and there is no indication, then: notify the first user that the tropic is trending; identify a second user action by a second user that relates to the topic; determine whether the first user has indicated a preference to exclude posts associated with the second user; and in response to a determining that there is no indication of the preference, send to the first user information associated with the second user action with a graphical user interface (GUI) element configured to enable the first user to interact with the second user action.
11. A system comprising: one or more hardware processors; and a memory coupled to the processors comprising instructions executable by the processors, the processors being operable when executing the instructions to: receive an indication of a first user action by a first user; and when the indication is received: analyze content of the first user action; determine a topic of the first user action based at least in part on the analysis; determine whether the tropic is trending; determine whether the first user has indicated a preference to exclude posts associated with the topic or a category associated with the topic; and in response to a determining that the topic is trending and there is no indication, then: notify the first user that the tropic is trending; identify a second user action by a second user that relates to the topic; determine whether the first user has indicated a preference to exclude posts associated with the second user; and in response to a determining that there is no indication of the preference, send to the first user information associated with the second user action with a graphical user interface (GUI) element configured to enable the first user to interact with the second user action. 19. The system of claim 11 , wherein: the first and second users are users of a social-networking system; and determining whether the topic is trending comprises determining whether the topic is trending across a portion of the social-networking system that is relevant to the first user.