When Dow Kim left his job in May 2007 as co-president of global markets and investment banking at Merrill Lynch & Co. to open a New York–based hedge fund, his timing could have been better. Expecting to raise $500 million to $1 billion in day-one money from Merrill — and hundreds of millions more from other investors — Kim quickly staffed up in anticipation of launching Diamond Lake Investment Group from Goldman, Sachs & Co.’s