Not public, but my company’s first acquisition was a failed integration due to bad communication. We went into it trying to be delicate with the target company’s employees and our leadership repeatedly told them they will be business-as-usual, but we still expected/needed them to integrate so there has been a clash along with extreme resistance from them.
The company I work for is the public company, so from that perspective, what I faced could be seen as one of the public examples of a failed merger. I experienced similar situations to what Erin mentioned above. We purchased one company, and we tried to keep important employees by promising them that they would be able to keep on what they were working on. However, we tried to change so many things from the day 1, and the important people left the company at the end.