This also applies to female friends as well.
I had a female friend in college that I worked with. I really thought we were going to be friends for a long time. Then I started noticing that she would act weird/rude/stand-offish when she was with her other friends. The last straw is when she brought her family with her (whom she would talk to me about all the time and show me pics of) to our office building. She looked right at me (I was at the info desk where we worked), looked around to see if anyone else was there, and walked right on by. A few days later, she saw me on the school shuttle, sat next to me and started chatting like nothing happened. During that conversation, she also referred to one our mutual acquaintances as ugly and started telling me about how desperate she was.
I went abroad and that was the last time I ever saw her. Kicked her off facebook and she had the nerve to message me multiple times and added me as a friend again. "Lol. Why am I not on your Facebook!?! What happened!!! Lol =)" "Hey lol". Are you serious right now? Had to get rid of FB because too many fake friends wanted to see what I was up to without actually being my friend. Puh-leeze.