Steven Senne/AP When Jack Welch turned the keys of the General Electric Co. Over to Jeff Immelt in 2001, GE was a well-run and greatly admired profit machine, stocked with exceptional management talent and innovative practices. Over the next 16 years, while Immelt held the top job, he completely demolished the House that Jack Built. Curiously, some now ask, what blame, if any, does Welch share in the disaster?