Social media impact assessment

A system for identifying influential users of a social network platform. The system may compute a score for each of multiple users. Such a score may be topic-based, leading to a more accurate identification of influential users. Such a topic-based score may indicate authority and/or impact of a user with respect to a topic. The impact may be computed based on authority combined with other factors, such as power of the user. The authority score may be simply computed, in whole or in part, directly from a tweet log without, for example creating a retweet graph. As a result, the scores may be computed, using MapReduce primitives or other constructs that allow the computations to be distributed across multiple parallel processors. Such scores may be used to select users based on impact as part of social trend analysis, marketing or other functions.