I don't think i've really had many friends sell me out.  I've had friends repeatedly cancel plans on me.  But i'm good at letting the right people get close 2 me.  Nobody really backstabs me, lies or anything like that. 
 
However, about 3 months ago, one of the theaters i work at had alot of problems with people being egotistical and acting really stupid.  The one director gave a speech about how some people need 2 grow up or move on and leave.  2 people who i consider my friends started telling people that me and my really good friend were who he waz talking about.  However, the 2 of us weren't even in the current show...we just showed up 4 the meeting.  On top of that, we both got asked 2 do the next show (b4 auditions) and also got casted in lead parts while the 2 backstabbers got smaller parts. 
 
I still didn't hold it against them.  I do my best 2 forgive and forget...i just don't allow them 2 get close again after doing stuff like that. 
 
Man, this post has me in the mood 2 pop in TLC's "What About Your Friends"...then "Case of The Fake People."