The thing you want to buy reflects a different way of thinking, which has value, but that difference is at odds with the culture you already have. Like an organ transplant, natural antibodies will fight against having the new organ fit in. And the more you do to force it in, the less of what you wanted to acquire in the first place remains. The vast majority of acquisitions fail for this reason. Few executives recognize the paradox, or think themselves immune to it.
Scott Berkun in The Year Without Pants: WordPress.com and the Future of Work