Gosh, there are so many levels to this discussion, really.
If you are totally out, and unconcerned with that sort of security issue, why wouldn't you have a face picture on a "Gay Fitness" site?
If you are in a profession in which being on any site, including match.com, which suggests you are looking for a partner, or implies you are open to hooking up, well, then, yes, of course, there are some security issues.
Then, of course, if you are in a so-called "monogramous" relationship with a man or a woman, and list yourself as looking for a "Hookup", you have more security issues.
The scenarios in the last two paragraphs imply that someone is doing some backstabbing, searching, sleuthing to find you, or they themselves are "trolling" these cruising sites.
That's all independent from X-rated pictures. For me, that's the only issue, but I can see why others would want to put their face pix as well as X-rateds (which RealJock now only allows WITH face) in the "Private Photo" section.