Apparently it put 10lbs on you - but whether that is fact or urban myth I don't know. I do know, however, that 'angular' people seem to take more flattering pictures then 'rounded' people, regardless of weight. It would seem the act of taking a photograph flattens the image and is kinder to angular shapes than rounded ones!
Really depends how the picture is taken: eg. from lower down, people look taller where as from higher up they look small. Perspective can play a large role too, so I'd fgure if a photographer wanted to make you look 'thin', they'd have a few tricks up their sleeves.
Going out today for a big ben replica to wear on my wrist! I always think that photos taken from slightly above, or from the same height with my head slightly dipped, makes my face look thinner. But might be kidding myself! And re. Ms Hurley, her particular posed photo stance is of course used for flattering purpose.