I was walking through the local markets here in Hoi An when this woman called me over to take a photo of her, making a big display and miming the snapping of a photo. I happily obliged. 
As soon as I took it, her smile reversed, she glared at me over her brow and began demanding a dollar for the photo. I explained that I didn't have any cash on me, so I showed her the screen as I deleted two of the images I took, hoping that would satisfy her instead. She lost it and yelled louder. 
Amused, and worried she may smack me with one of the many dead fish from the next door's stall, I very bravely backed away.