Shibuya Panhandling

I have always been proud to say, “There are no beggars in Tokyo.” But two incidents in the past month have made me a liar.
The first took place at Shibuya station a couple of weekends ago. Tod was buying a ticket for the Hanzomon line. When I looked to see if he was done, there was a balding man dressed in grey pants and a blue jacket talking to him. He looked like a do-gooder trying to help a confused tourist with the machine. I saw him talking to a different foreigner as we went thought the wickets a few minutes later. When I asked Tod about their conversation, he said the guy asked him for 500 yen. In English.
The second incident was also at Shibuya. As we passed along the street from the Hachiko side to the Toyoko side of the station last night, a filthy, dreadlocked rag-man got a bright look in his eyes and shambled in our direction. I watched in my peripheral vision as he walked along with us for a couple of steps, face angled toward us in a hopeful way, before he gave up and stopped. He didn’t try this with any of the gazillion Japanese also walking along that way.
So it seems that foreigners are being targeted by panhandlers in Shibuya. Has this happened to you? What did you do?