You will, no doubt, remember the story of Kristian Saucier. He was the young Navy sailor who admitted taking a few photos of his submarine so he could show his family what he did in the military. The photos contained some relatively harmless classified information, were never shared with anyone, and led to his prosecution and conviction, his "other than honorable" discharge, and a year in prison.
In case you've forgotten the details, here's the report from the Guardian...