Unfortunately in most poorer countries I've been to, a lot of the people have found that they can charge tourists for taking photos of them... In Peru they were dressing up in native costume with llamas, waiting for a tourist to take their photo to demand money. It just adds to the hassle factor.
I made sure never to take a photo of someone & their llama for that reason, but did take some pics of people from far away with a telephoto. We did ask a bunch of porters on the inca trail that were resting on a rock if we could take their photo - they agreed, one guy covered his face.
Or in vietnam they dress up as a cowboy or as a monkey and wait for you to take their picture to ask for money. It's awfully odd.