Vigilance and self-policing, because you're right, regulation on this front has a highly chilling effect on expression.
This particular topic is near and dear to me - I do a lot of street photography which is, at least partially, defined as taking pictures of strangers in a documentary manner, and almost always takes place in public.
Countries with strong privacy laws, such as France and Japan, do suffer from this. The photographic community in the UK has been hit hard in the past few years as even innocuous picture-taking of popular landmarks has been hit with intense police scrutiny if your gear is too "good".
We do not want the heavy hand of government in here, because inevitably this will mean throwing the baby out with the bath water. Expression and art is usually at the boundaries of what society currently finds palatable, and activities along this border needs to be regulated by people, not immutable and slow-changing laws.
The only solution I can think of (and it's not a particularly good one) is to slam the door shut on people who would abuse their freedom of expression and whose actions will lead to the loss of freedom by inviting regulation. I'd rather oppose people rather than technology, though.