You have absolutely no idea what a person with just a little bit of bad will can do with just the help of any search engine.
I'm not to eager to show my picture anywhere, because basically, everyone who needs to know what I look like will sooner or later meet me face to face.
But I'm definitely unwilling to end up as a search result on images.google.com
"Witness protection program"? How about privacy! Self-determination. The freedom to decide what happens to pictures of mine?
That's all.