Passing on unkind comments about their "friends".
I have recently found out that someone I considered to be a friend was speaking to his friend (an acquaintance of mine who I have met twice) and discussing me, not in a nice way. He then repeated this conversation with other friends, and it eventually got back third hand to me months later.
Am I unreasonable to expect someone who I would call a friend to not then keep spreading these rumours, but to either say nothing, or speak to me directly and ask me what happened, and check I was ok.
I couldn't really care less about the original guy who was spreading these rumours, as I have said he is an acquaintance not a friend, but I am disappointed in the guy I considered to be a friend.