That’s a sin in childhood games but not, it seems, in the grown-up world of finance. JPMorgan sold a triple-leveraged investment in Fairfield Greenwich Group’s Madoff Ponzi and, to show its good faith, put in $250 million of its own money. Then, early last fall, JPMorgan grew suspicious and pulled all of its own money out and went home but didn’t warn its investors. They stayed in, lost everything, and now they’re mad. JPMorgan’s behavior wouldn’t pass muster at Tiny Tots Nursery School- it probably will on Wall Street. Bad boys.