1. A method comprising the steps of: identifying a set of events, one or more of which are captured in images from one or more cameras; generating a plurality of similarity scores, wherein generating the plurality of similarity scores comprises, for each event in the set of events, generating a set of one or more similarity scores; wherein each similarity score in the set of similarity scores that is associated with an event of the set of events (a) is relative to another event, and (b) reflects how similar the event is to the other event; identifying a feature set of a target event; determining probable matches to the target event by: determining similarity between the target event and only a particular subset of the set of events; wherein determining similarity between the target event and only the particular subset of the set of events is performed by comparing the feature set of the target event with only the feature sets of the events in the particular subset; wherein the particular subset includes less than all of the events in the set of events; from among the events in the particular subset, determining that events in a first subset of events of the particular subset are probable matches to the target event; wherein the first subset of events includes less than all of the events in the particular subset; wherein the first subset is determined based, at least in part, on a similarity between the feature set of the target event and feature sets of events in said particular subset; and after determining that the first subset of events are probable matches to the target event, determining which events in a second subset of events are probable matches to the target event; wherein determining which events in the second subset of events are probable matches to the target event is performed based how similar the events in the second subset are to events in the first subset, as indicated by a subset of the plurality of similarity scores; wherein determining which events in the second subset of events are probable matches to the target event includes determining that a subset of the second subset are probable matches to the target event; wherein the step of determining that a subset of the second subset of events are probable matches to the target event includes determining that a particular event is a probable match to the target event without comparing the feature set of the target event to any feature set of the particular event; wherein the method is performed by one or more computing devices.