About a year and a half ago, the sleepy state of South Dakota found itself rudely awoken by the global spotlight. In a filing for his Hong Kong-listed company, Sunac, Sun Hongbin, the Chinese real estate tycoon with a net worth around $10 billion, disclosed he had just transferred his shares to the South Dakota Trust Company. To the surprise of most analysts, a small, two-story brick building in downtown Sioux Falls was the proud custodian of a chunk of shares that is now worth more than $6 bill