Karen Fenner, New Jersey, USA

A Because you can't number-crunch culture.

And financial analysis is almost always where merger evaluations begin, along with some level of strategic analysis. If those assessments seem positive, a cultural comparison of merging companies might take place. Might . . .because by the time a merger starts to appear attractive, deal heat has already started to creep in, and the ability to back away has started to creep out.

You would think with all the merger and acquisition activity in recent years that companies would have figured out how not to succumb to deal heat. Some have; many haven't. Blame human nature.

Blame investment bankers. Blame the fierce competition of the global market. Whatever. Too often deal heat is inexorable, especially if there are other contenders in the ring. One result is the 'sin' you describe: a disregard for cross-cultural differences between merging companies. But in the mad dash to the "nish line, lots of other M&A mistakes get made.

Perhaps the most painful is the reverse hostage syndrome, which happens when an acquirer wants a deal so badly he ends up making concessions that are regrettable at best and destructive at worst.

Indeed, in many reverse hostage situations, the buyer gives up so that ultimately the acquired company can't really be considered acquired at all. It's still calling all its own shots . . . from its strategy to its staf"ng decisions to its core values.

As for relations with the new owner, reverse hostage businesses tend to act like they belong to a separate country . . . and a hostile one at that. They rebuff any suggestions for change with brush-offs like: "You don't understand this industry. Just leave us alone and you'll get your earnings at the end of the quarter."

No wonder most 'owners' are left to wonder, "Why did I pay all that money for nothing?"

A classic case of reverse hostage syndrome is playing out at the headquarters of Boston Scientific. It began in 2004, when the company paid $742m to acquire Advanced Bionics, a California company that makes implantable electronic medical devices. At the time of the purchase, Advanced Bionics was losing money but Boston Scientific was convinced the business could deliver outsized returns. And maybe someday it will. But now Advanced Bionics and Boston Scientific are slugging it out in federal court.

At the heart of the case is a concession made during negotiations. Alfred Mann, owner of Advanced Bionics, insisted on staying on as leader of his company.

An overheated Boston Scientific said yes. Maybe its senior executives thought Mann, who is now 81, would retire soon. Maybe they thought he would let Boston Scientific have a say in management. Or maybe they thought Mann would lead the business to profitability.

None of those things happened.

And so, last July, Boston Scientific asked Mann to resign, saying he was resisting the changes necessary to make Advanced Bionics a moneymaking enterprise. Mann refused to leave, saying his contract allowed him to run Advanced Bionics for as long as he wished. A federal judge agreed with him . . . a decision that is now out on appeal.

If you can't buy a company on your terms, fight the burning desire to forge ahead, or at least build in some kind of protection. No one likes being held up. But the reverse hostage syndrome, which can paralyse companies and undermine even the most promising M&A deal, comes with an added insult. You're being robbed with your own gun.

Jack and Suzy Welch are the authors of the international best-seller Winning. You can email them questions at winning@nytimes. com