There are few sales ploys more effective than having the adorable, smiling-though-still-somehow-sad child in tow. The book-and-bracelet barkers on and around Bui Vien street practice this tactic with unapologetic charm and finesse. Unless you have a heart of stone, it’s nearly impossible not to feel the tug of making just one small sympathetic purchase (old women and limbless men are similarly hard to resist). After all, it’s only a couple of dollars — “Good price for you!” — what can be the harm? The danger is that once you’ve made one such purchase, the flood gates of your benevolence are now thrown open and the rest of the knickknack charmers will smell your weakness and flock to you with relentless tenacity. There is no certain tactic that will turn them away.