One can argue this is a battle between good and evil, where LinkedIn is the good guy and Facebook is the bad guy. I only say this because of the difference in the dynamics people generally use each of these networking sites. Facebook is generally a more laid back social setting that is lighthearted and more of a living room atmosphere. People tend to be careless about their status updates, pictures and reposts. LinkedIn is more a a formal and professional environment where people are networking more with businesses and personnel in their areas of aspiration. Both sites are very beneficial for professionalism, but I don't believe many people realize that many employers use Facebook to investigate how potential employees are on a personal level.