Same here. There is something to be said about taking the high road and avoiding confrontation regarding unimportant issues but to lose friends due to gossip (the question being how good of a friend were they?). Stay strong in knowing that you can confront those who seem to make you feel this way, just be sure something is really being said. At work I would often observe and follow through with the way I was being treated. If the co-worker kept up with being a know it all or going to the boss with each and every issue I would work harder and make sure the boss could see what I was doing. Then, make sure I talked to the boss more and got know his/her hobbies and values. Eventually you can play the same game with the gossipy know it all and squeal on them from time to time and correct them as they will slack off (I promise) as you work harder because there will be less for that person to do.

If were talking kiddie friends then it is much the same. If you know a good friend and they are falling in with the bad people be sure you get to know the bad friend and try to be the cool kid. Then make sure your friend sees how you are changing and tell them you think it's wrong but what should you do and your friend (a true friend) will ask you to change and come back to being normal. If not you will need to make the changes yourself and hope the good friend follows you along.

AND....if your paranoid a lot be sure you seek therapy so that it does not grow into full blown psychosis.