It’s the rare C.E.O., of course, who’s comfortable presiding over a shrinking empire, and running a public company creates a bias toward action, if only as a way of convincing investors that you recognize your problems and are dealing with them. But history suggests that, when it comes to mergers, the best response is often to just say no. In effect, deals like the CNET acquisition are a bit like an aging outfielder taking steroids in order to stave off the boobirds. The difference is that steroids usually work.