The exhibitionist strips down, takes a photo containing a shiny object somewhere, and then posts the photo in a public online forum. Some reflectoporn is true fetish -- it gives the exhibitionist the same thrill as flashing strangers in public -- but much of it is done as a joke.
Typically, reflectoporn is posted in the form of an eBay auction item. The listing is for a tea set and includes lots of high-resolution photos. And then after the photos get passed around by giggling bloggers all over the world, the auctioner claims to be "shocked and embarrassed" to learn that -- oh, no! -- the highly-polished silver teakettle <i>actually</i> reflected his willie! And right when he just happened to be fondling himself, too! Talk about awful luck!