Yeah, I've started asking this during a punt, too.
Only worked once so far, and the camera on my punting S3 takes a decent enough photo. The girl wanted to see them and there was one she was a bit iffy about, so I deleted it there and then. She was happy with the rest and my promise that they were for my eyes only, although she asked if I'd shown them to anyone next time I saw her. I just put on my hurt, innocent look and said, 'I wouldn't do that after I promised not to.'
I keep them on the phone and back them off to a 16gig USB stick. Overkill, I know, and I'll never fill it up, but I got it free from work. I'd seriously consider an extra £10 for candid face unhidden photos, but not the silly £30 -£50 I've seen demanded on profiles.