Once, I had a friend that I thought was my very best friend in school. I went to college, and despite the fact that I would call her or e-mail her, she would not return my messages. There was even a time that I was home for a long weekend, so I called her as soon as I was home, and asked her to call me back so we could do something together.
Did I ever hear back from her? Not till the night I went back to school, and even then, she just left a message on the answering machine, which was something to the effect of, "Well, I didn't call, but I figured you'd be back at school already."
Stupid excuse, I thought--even if she couldn't get together with me that weekend, she could have at least called and said, "Hey, it's cool that you're home, but I'm really sorry--I already have plans." At least do the courtesy of realizing that friendship is a two-way street, and I can't be the one to always maintain the relationship.