Big Fat Jerk

I am now going to describe a natural phenomena that occurs to many people...

You know when you're in hurry and trying to walk somewhere as fast as you can? Then all of the sudden you see someone that you kind-of know. It's not like you're really friends, but you are kind of old acquaintances really. But the point is, you don't know them that well, so when you see them you have to make the split second decision: acknowledge them, ignore them, or pretend you didn't see them. Now for me, the latter was impossible because we made eye contact. But in that moment I thought both of us had made the silent pact that neither of us would say anything. So I turned and began running down the stairs. The problem was that he didn't get the memo. He yelled my last name (probably because he couldn't remember my first name, which I'm really not offended about) and I turned out of habit. I gave a very awkward wave and an even worse half smile before turning back around and promptly running away. What is wrong with this picture? Well not that much, except now I look like a big fat jerk because a) I didn't say hello first and b) I didn't stick around to make small talk. Why do people have to break the silent pact of non-acknowledgment!?!? Life is so much easier when it is followed people!