When I arrived in Los Angeles, I was told time and time again that most people here are nice and fake. While I was surprised by just how laid back people are, no one gets too upset and no one is overtly rude, I have not witnessed any violence or even harsh words. Over time I was able to understand what those initial warnings meant.
The entertainment industry here is wrought with people who are looking to see how they can climb the ladder of success. In order to become gainfully employed, you need to be likeable, have a great work ethic and be willing to do anything your boss asks of you.
This is where the fakeness comes in. You will find people who are smiling even though they hate the world. You'll find people who will agree to be friends with you, not because they like you, but because they believe knowing you will help them to prosper.
There is also a concept that I learned about called mirroring. Someone who is interested in gaining your approval will mirror your style, interests, speech patterns and activities. I saw this first hand when one of my roommates was having a conversation with another roommate and he pretended to like a certain cartoon so they would have something in common.
One man I met who works for a production company told me, "Success here is 20% talent and work ethic and 80% kissing ass and making sure everyone likes you."
The benefits of being fake in LA is you'll be gainfully employed longer and will get to work on awesome projects. The drawbacks of being fake in LA is you will be easily forgotten as a follower and you won't be respected as a leader if you don't have a firm opinion to share.