It's a ridiculous idea altogether. A cypherpunk just wouldn't go if they really didn't want cameras to see them there. I find it bizarre, unless there are specific rules that ban it and people do it anyway. If the rules allow it, you have no moral superiority. Everyone agreed by choosing to be there. I don't personally take pictures of anyone without asking, even in public, but I would never expect other people to be the same at a conference that allows it. I just wouldn't go or cover my face if it was that big of a deal.