On my experience. The answer was yes. That's true that the true friends are hard to find because some of friends are not true. They pretend you as a good one but if you are not infront of them they bit you at the back.
I have been lucky because I have got some really good friends, however it is pretty hard to find them, and there have certainly been periods in my life when I haven't found any of my friends to really be 'true'.