There are partnerships in companies all the time. Look at the biotech and hitech industries. There may be two, three or four companies sponsoring the development of something. If it takes off they all get a piece of the pie. But if it fails they share the pain. It is a way of minimizing risk.
Yes,there have been buy-outs of companies organized by two or more companies. But there are potential antitrust issues. Search "Wiliams Act" on this board, I think I may have posted some inks to some articles about it.