The word may seem childish, but I think it's appropriate. Chances are, most of us with atheist connections know at least one "poser", who seems to call themself atheist just to be edgy, contrary, and different.
This happens in theism too, and has a lot to do with how people want to identify themselves (rather than what sounds the most logical, unfortunately). For us atheists, these "fad" atheists are not helpful. They're uninformed, crude, angry, uninformed, antisocial, and uninformed.
And when you grow up in a religious area, as many of us had, people are not prepared to accept our atheism. The other day my mom informed me that I merely believed what my brothers believed because I wanted to fit in with them. The joke is on you, Mom! They still don't like me!
So it raises two questions: What is your reaction to atheist posers?
What do you do when someone thinks your beliefs cannot possibly be grounded in fact?
I once watched a self-proclaimed atheist argue on the bus. I did believe he was an atheist, but his only real argument was something about there being no horses in the Book of Mormon time/place. This basically ends with him being somewhat outcasted, his friends being firmer in their own beliefs, and likely a rocky religious/nonreligious road for this young man. I didn't say anything, perhaps I should have. I'm hoping I made up for it-- when my own friend found out about my atheism, I knew she would bring it up. Therefore, I tried to sit in a place where this kid could hear the discussion. Low and behold, she did, and we had a friendly debate which went well. I have no idea whether he was listening, but I hope so.
I'm confident in my beliefs so it doesn't worry me that much, I just do my best to prove that I'm kind, intelligent, and know what I'm talking about. What are your experiences? I'm curious to hear. Atheism is so diverse, with only one real thing in common, so you can't always tell what your relationship with another atheist is going to be. Any really bad atheists out there? Story time!! :D