I see your point, nothing is 100% effective. Especially anywhere more than 4 or 5 people gather. I would think the first year of implementation would be more of a 'let everyone know' type deal. And the MC can also point out any changes in policy (not just this one) during breaks.
However, with the lanyards/whatnot, the instances of unwanted photographs should go down. If you don't wear a badge/lanyard/etc you won't really have to worry about it. I'd suggest we have an addition to the policy that basically reads "We understand that many people will not know about this policy, and on a first incident someone taking an unwanted photograph is told about the policy. Afterwards, the case(s) will be handled as determined by x." There should also be a part that says "If the lanyard/badge/whatnot is not clearly visible, the picture taker should be informed of the issue and remove the image from the phone/camera." No one can control what happens to participants outside of the venue, unfortunately, but hopefully other Code4Libbers would still abide by the policy.
This isn't meant to restrict your freedom or get people in trouble. It's to protect those who feel they need protection. I wouldn't use a lanyard/badge/whatnot personally (if voluntary - if you have to choose a color on registration, obviously I would), but I'm not going to make others feel as though they're in the wrong for choosing to do it.
Did all of that make sense? 
Sarah
 
> Date: Mon, 26 Jan 2015 08:52:18 -0800
> From: [log in to unmask]
> Subject: Re: [CODE4LIB] Conference photography policy
> To: [log in to unmask]
> 
> On Mon, Jan 26, 2015 at 6:58 AM, Galen Charlton <[log in to unmask]> wrote:
> 
> > I would like to propose that C4L adopt a policy requiring that consent
> > be explicitly given to be photographed or recorded, along the lines of
> > a policy adopted by the Evergreen Project. [1]
> >
> 
> As a practical matter, this is functionally equivalent to prohibiting
> photography except for arranged photos which will need something simple
> (like pictures of  cameras and mikes with slashes through them posted
> throughout the venue) to communicate the policy. Differential badges,
> lanyards, etc will not always be visible, and not all people will notice
> them, be aware of what they mean, or can be assumed to be familiar with a
> written policy. On an aside note, a lot of activity occurs outside the
> official venues and it is in these areas where people might be most
> vulnerable to unwanted photos.
> 
> kyle