Les Difficultés de Communication

When my brother and I talk to each other, we go from Dutch to English and back again five times per sentence. We've grown so accustomed to both languages that we aren't consciously aware of which one we're using at any one time. This can make for amusing situations, as was confirmed yet again today.
We were on this bus, talking. I whipped out my camera to take the above shot, and it really startled these girls. They seemed offended, but unsure as to how to communicate this to us. It took me a while to figure out that apparently, we'd been speaking English exclusively, and they were under the impression that we weren't Dutch. I'm not sure why some people get nervous or even take the piss when they get photographed, but coming off as foreigners sure proved a very effective way of bailing out of such a predicament.