Kraft management predicts that the $50 billion combined company will be able to save $675 million over three years, but that’s not the primary reason for the merger. It’s all about global distribution and access to developing markets. Cadbury has it, Kraft wants it. Makes sense on paper.

Most mergers do make sense on paper, yet many become spectacular failures. The reason? A lack of appreciation for just how difficult it is to integrate not only global operations, but two proud and independent workforces.

Kraft is going to face this problem in spades with Cadbury. Todd Stitzer, Cadbury’s CEO, said that Hershey’s would have been a better cultural and operational fit. The company’s Chairman, Roger Carr, took it a step further by saying Kraft is “an unfocused conglomerate” with “unappealing categories” and management that “underdelivers.” Carr went on to say, “There is no strategic, operational, managerial or financial reason” for the merger.

Sure, Carr’s statement may have been a bit of strategic bluster to raise the value of the offer (which he succeeded in doing), but it sounds pretty categorical to me. And it was telling that not a single Cadbury executive was present on the conference call with analysts to discuss the deal. Hmm.

Kraft estimates it will take $1.3 billion to “integrate Cadbury.” I’m not sure exactly what that means or who came up with the number, but I don’t know how anybody could forecast the costs associated with the fear, resentment and internal jockeying with which Kraft and Cadbury managers and employees are now having to deal. The fact that Britons consider Cadbury a national treasure that has been overrun by ugly Americans sure won’t help.

Let’s hope Kraft doesn’t end up with a stomachache.