I've been scammed before (petty scams, like being charged more for something that locals pay, etc), so I tend to have my guard up even though I travel quite a bit.
When I visited my brother in London a couple of years ago, we decided to make a side trip to Belgium. I had taken French and know the basics, and my brother, even less
) but I can read better than I can speak French.
We spent all our Euros by our last day on food and chocolates. We packed our stuff and checked out of the hotel and decided to walk around town and walk back to the train station for the afternoon return. I guess we stood out as tourists because we each had a backpack on (and cameras, though I only take it out when I see interesting stuff). We are also of Asian descent, and we didn't notice a huge Asian tourist population there.
In any case, I was fumbling something in my pocket while my brother walked ahead. In the few split seconds, a bunch of school-age girls came and surrounded my brother and kept thrusting some papers at him. My brother kept saying "no, thank you." and "no, I don't speak french"). My brother is (athletic, almost 6 feet tall) and while I am much smaller, I tend to be more firm on things.
I had my guard up and walked over and asked what's going on. They tried to explain in French, and I didn't get it. When I looked at their piece of paper, there were some words on it and I read it to understand that they were asking for our autographs.
It was no harm done, so we autographed it and they were happy and went away.
Further down, another older group of teenagers ask if they could take a picture with us.
I get the impression that they are doing something for school, so we entertained it. My brother is loving the attention, so we grinned and took a picture with them, they thanked us and we went along our merry way.
I didn't know what was going on at the time, but my scam radar did go off and I checked to see if anything was amiss. I had read that in some places kids can surround you and steal stuff from you while you're distracted. We just checked to make sure we still had our passport and cameras (the rest is just travel stuff, whatever) and all was good.
While we were somewhat confused at the time, I think they are doing some sort of school assignments (probably requiring them to meet tourists or get proof that they met with some tourists), and we apparently stood out like sore thumbs.