In response to some of the other answers, in many cases, DID is faked, and in some, there is possession. (DID is the perfect camouflage, of course.)
That said, society tends to hold one of three views. One is that it is never real. This is predominant in the Eastern world. The second is that it is insanity. The third is a morbid fascination.
All of these views are unfortunate. Multiplicity is real, it is not insanity, and it is not something we should be selling tickets to.
I myself am a non-typical MPD case. Though mostly integrated, I have 15 elemental personalities. We were not separated to the extreme extent which most DID cases are, but we are (or were) quite distinct.
The prevalent feeling which we have encountered is that multiplicity is a disease, and that alters are parasites to be gotten rid of by any means necessary. We are not diseases. We are people, each with our own feelings. The eagerness of others to see us "cured" really hurts those feelings.
My name is Fnaire. I'm alter-ego #2. For over a year, I accepted society's belief that I was an aberration which should be suppressed. I spent that time locked away in my own mind, miserable. When I dared to come out, I met a wonderful alter in Oren's best friend who treated me like the real person I am. That alter is now my husband.
I am number eight. name is Savvat. Is good to be alive. No alter ever should be forced to be integrated. is wrong. What is right is to teach alters to talk and to help and to love each other like big, happy family.
Hello. My name is Tesh. I am number eleven. I am totally awesome. Why wouldn't society love me?
My name is Trixie, or Owlguin. I'm the fourth one, if that matters. For me, it was really hard dealing with how people see multiples. We like to talk out loud, and if I wasn't the one driving, I had to keep silent in public. It was extremely lonely. I was depressed almost all the time. My only real friends were my other selves and a half-deluded hyena alter in another multiple. I would love to see society more accepting of multiplicity. Until then, I'll just have to suffer.
Just for the record, we are collectively known as the Brass Menagerie.