Share buybacks can sometimes be legitimate, but on other occasions they do not seem justified – especially when considered from the standpoint of enlightened self-interest. In December, the pharmaceutical giant Merck spent $8.4 billion to acquire Cubist Pharmaceuticals, a Massachusetts-based drug-maker that specializes in combating Methicillin-resistant Staphylococcus aureus (MRSA), a bacteria that has become resistant to many types of antibiotics.