This version of jpeg is called jsteg. I've used it to
decode some jpegs I had at the time on the harddrive
(mostly anime-manga related), and to my surprise every picture I tried gave some output, sometimes bigger, sometimes smaller. Anyway, they were just sequences of bytes, and there were no signs of readable text in it. In the jsteg documentation they suggest to encrypt the text before including in the image. So or it was just some garbage (an unavoidable side effect of the used algorithm, maybe), otherwise it was some encrypted text, in this case this would be a widely used way to send secret messages which is unknown to most.
Varthall
