At what point do multiple personas for social context cross into multiple personalities disorder? Recently I took part in a conversation about the difference between the "many hats" of a successful corporate executive, and "multiple personality disorder." Although humorously bantered, the ideas shared in that conversation shed a light on the fuzziness between when consistent multiplicity of personality characteristics is useful and good (to better adapt to a variety of environments), and when is it counter-productive or self-defeating, and labeled multiple personality disorder? What are the "cross-over" points?  

Multi-tasking in executive management positions require being able to speak in the vernacular of many stake holders and to be able to communicate effectively with a wide variety of groups and collaborators. Corporate cultures vary between industries, countries, even regions, and size of the enterprise, etcetera, and yet, a successful corporate executive can walk in any of these with ease. How can the effective use of these "chameleon expressions" be distinguished from split personality?

I use this example tongue in cheek, but Mitt Romney is the perfect example of someone whose personalities clashed in company with one another (fund raiser, 47% vs. 100%). He is a very successful businessman, did his changing faces in the media unravel a persona that didn't really exist?
I think the difference comes down to awareness and control. A person who "wears many hats" and can step into different archetypes is a sort of personality chameleon, whereas a person with dissociative identity disorder has little or no control over changing personalities, and certain personalities within that person may be only partially or completely unaware of other personalities.