Call me what you want but I just read the minecraft wiki on the "herobrine" and im pretty sure its not real but it still scares the crap out of me.

Anyone care to give their opinion on it?

Yeah, it's obviously not real. They're called "creepy-pastas". It's basically made to scare or sometimes to just intrigue people.

I personally like reading these, if the writer has any idea about what he's going for. This particular one, not so much. Mostly cause the ending was pretty bad.

I mean Notch's dead brother is haunting his game, but he only appears to a small number of absolutely random people. Why is that?

It was a clever and creative creation by the community, no more, no less. Nevertheless I found some of the YouTube videos made "documenting" it pretty amusing!