The strawberry vendors stand on street corners throughout Palo Alto, at busy intersections, outside shopping centers and banks. Cars slowed along Stanford Avenue on a recent afternoon, their drivers peering at one vendor's succulent strawberries, mangoes and cherries. A woman stopped her vehicle at the Wellesley Street intersection as drivers behind her swerved to go past. "How much?" she asked the vendor. "Ten dollars," the man said as he passed a box of fruit through the car window. But behind the sweet fruit there is a bitterness, a story of indentured servitude playing out on Bay Area streets. According to...