Backstabbers

I came to know yesterday about some people whom I was quite paly with, do not speak favourably of me. I mean...O.K. I don't even expect everyone to like me, but at least do not make a show of being a great friend of mine when in your heart you don't have the same regaurds for me? Why to live life like a hypocrate? How will you explain such a behavior?? What are they afraid of and what do they want to proove by behaving like this?