1. A method involving an apparatus, the apparatus having an image capture system including a first optical portion used in capturing image data from a first side of the apparatus, and a second optical portion used in capturing image data from a second, opposite side of the apparatus, the first and second optical portions having parallel but not coincident optical axes, the method comprising: (a) sensing a user action; (b) in response to said sensed action, activating the first optical portion to capture first image data from the first side of the apparatus, the first image data depicting a subject; (c) activating the second optical portion to capture second image data from the second side of the apparatus, the second image data depicting part of the user; (d) computing a hash based on the second image data; (e) storing information including at least information based on the first image data, and said hash; and (f) consulting database information comprising stored data for plural different persons, to attempt to identify—by reference to the stored information—the user.