I was catching up on this thread and ran across this.

We were in Shanghai late last year and as we wandered around the Bund we were approached first by a young woman alone. Like others, we've taken photos of others and had photos taken of us in various parts of the world.
I took her photo and soon dismissed her fairly brusquely after she started the "Where are you from?" routine. Mrs. Fredd thought she was on the level at that point and rebuked me for being impolite as we walked away.

But soon we were approached for a photo by a couple, then by another couple, and at one point by a group of four or five. Mrs. Fredd realized her cynical husband was right this one time.

Some were standing at subway entrances clearly waiting for foreigners to show up and after the first young woman it became hilariously obvious what was up. It happened to us no fewer than five times in the space of little over an hour.

It's a good come-on and we'd never seen it before. Sadly, it will probably spread elsewhere. They've certainly saturated the market around the Bund.