1. A system for automatically checking out an object, comprising: a scale subsystem for measuring a weight of the object; a visual sensor for capturing an image of the object; a visual subsystem coupled to the visual sensor, wherein the visual subsystem is configured to: i) extract multiple scale-invariant visual features from the image, each of the multiple scale-invariant visual features having an associated feature descriptor defined by a feature vector; ii) compare the extracted feature vectors to a plurality of feature vectors associated with a plurality of known objects, each of the known objects having multiple ones of the plurality of feature vectors associated therewith, and iii) identify multiple ones of the extracted feature vectors that match a subset of the feature vectors associated with one of the known objects; and a check out subsystem, coupled to the visual subsystem and the scale subsystem, configured to identify the object based on the matching feature vectors and the measured weight.