BANKING: Trustbusters' Retreat

For a year, in the Manhattan courtroom of Federal Judge Harold R. Medina, the U.S. has been trying to prove that 17 of the nation's top investment bankers and the Investment Bankers Association, to which the 17 belong, conspired to monopolize the underwriting of new security issues. Last week the U.S. dropped the charge against the I.E.A. As Judge Medina indicated, it might just as well have dropped the case against the 17 bankers, too. Said Judge Medina last fortnight, after many criticisms of the Government's sloppy presentation: "You would think I would begin to get an inkling of how it is all these firms connived together. I have not seen a thing."