Here is a post by Professor Bainbridge who refers to arguments in the pending Sallie Mae buyout litigation in Delaware Chancery Court and a paper by 2 economists,  to support the position that fairness opinions given in M & A deals are not worth much due in part to the perception that they are intended to seal the deal as opposed to providing an objective evaluation of the deal. Here is a prior post on this blog linking to the pending Sallie Mae Chancery Court case where the issue was raised at a recent hearing.