The only cart I've seen, was in San Francisco. They were right in the middle of tourists, beaming with big smiles. These were not the shrinking violets that most everyone has been talking about. I think the Brother was enjoying the attention cause he actively engaged people.
So there is always a rogue JW willing to go the extra "smile" despite what the guidelines are. Unless of course, the powers above decided that San Fran was a great place to actively barker their wares.