Dave Bing has just signed on to four years of maybe the most futile and thankless job in America: mayor of Detroit. What in the world was he thinking? "I wouldn't have taken this job if this wasn't doable," he tells me. "I finished basketball in 1978, then went into my own business in 1980 and did it for 29 years. . . . Now I get to the end of that career and probably should have retired. But there was a calling greater than anything that I ever envisioned, and that was to help bring this city back." In...