1. A machine-readable medium having no transitory signals and storing instructions that, when executed by processing circuitry of a machine, cause the machine to perform operations comprising: receiving, by a mood detection system comprising the processing circuitry, a request from a computer network to monitor attendee sentiment at an event, the event including two or more attendees; receiving, by the mood detection system, from a plurality of client devices over the computer network, a corresponding plurality of messages from respective social network members to a corresponding second plurality of social network members, each message including an indication of a position of the client device of the social network member and an indicator comprising at least one of an image of a face of an attendee or a description representing an emotion of an attendee; assembling, by the mood detection system and based on the respective position indications, from the plurality of messages a set of messages that were received from social network members at the event; determining, by the mood detection system, a numerical value for each of the indicators in the assembled set of messages, numerical values for each of the images of a face determined by defining points for one or more regions of the respective faces and comparing a distribution of the points with points defined in an electronic database of facial expressions; aggregating the numerical values to determine an aggregate mood of the attendees of the event; and displaying, on an electronic display, by the mood detection system, a graphical representation of the aggregated numerical values.