Absolutely. I have been backstabbed too many times to count because when I see someone who needs me, I help all I can. Just recently I had a girl whom I met thru playing Yu-Gi-Oh years ago and she was going thru a rough time with her cheating boyfriend. We became best friends when I helped her take her car to be reposessed because of her boyfriend. Later, I helped her pay her half of the rent to her boyfriend so they would not be evicted, which was a loan to be repaid, but never was. Then later, he lost their apartment home because he did not pay rent and she wound up moving in with me, rent-free, because she lost her job. Now, all she did was sit around on her butt, surfing the web and watching MTV all day while I worked hard and hardly ever helped. Oh, did I mention because she had no job, she couldn't pay for her cell phone or her probation costs? I paid for those as loans. Then, guess what, she went back to her deadbeat boyfriend after breaking up with him for the thousandth time and moved out on bad terms with me.
FastForward ahead 6 months. I met my current fiance and she knew I was still in touch with the former rooommate/best friend. The former roommate was going thru a rough time and realized she made a huge mistake by moving out. All of her friends and most of her family told her she needed to talk to me. Well, she did and I laid down some new rules and my fiance offered her to move back in. So, she did. Then went right back to her old ways and moved out once again. Guess how many true best friends she has now? NONE.
I agree about if you have something to say, say it to your face. I have never said anything behind someone's back that they haven't already heard me tell them to their face.
So, yes, I think we have all been stabbed in the back at some point by someone who claims to be a friend or a best friend. My advice to you, move on. You do not need, or want, or deserve a "friend" like that bringing you down.
Z