U.S. stocks are little changed in late Monday morning trading, with the Dow Jones Industrial Average and the S&P 500 up 0.05% and 0.25%, respectively, at 12 p.m. EST. Shares of Pfizer and Allergan PLC, meanwhile, are down 1.86% and 2.43%, respectively, as the companies announced they are merging in a blockbuster deal with a combined enterprise value of roughly $160 billion, capping what was already a record-setting year for pharmaceutical industry M&A. Investors appear to be taking a dim view of today's merger announcement, with shares of both the acquirer and the target declining. This columnist believes the market has good reason to be skeptical. Earlier in its history, Pfizer was thought to be a smart and skilled acquirer.