I think the worst risk of posting your pic, or kid's pic here on the DIS is being recognized by a fan (another DISer) at the theme park or in person on your daily travels (i.e "Hey I'm So and So from the DIS boards are you Blah Blah Girl?"). That would just be a problem if you are the type of person who does not like to be recognized. Then again, if you are that type, you're probably not posting your picture here.

Still, I understand that everyone has a comfort level and I respect that.
As far as safety - electronic and otherwise, the world of technology has forever changed that ability to alter photographs. If you are worried about having a photo altered, that can happen anywhere. Even during the horse and buggy days

when I was in highschool, our Photography instructor taught us how to alter and create visual effects with photos. The invention of the cell phone camera has taken away anonymity as we knew it, forever. It is the laws governing the use of the camera phone, etc that determine the extent of protection against exploitation.
Child predators want easy access with anonymity. They are cowards. They don't want to stand out in a way that draws attention to themselves. Technology always involves the risk of a wire trail (hey, remember, Big Brother's always watching, but there's an up side to that!). I would be more concerned about people that could potentially have close, regular (and potentially undocumented) access to my kids and gain their trust like teachers, ministers, family friends and other individuals they interact with on a daily basis. I think the best defense is a good offense - just try to keep tabs on your kids as much as possible and stay into their business.