I agree that staring is the worst thing to do.. I have personal unfortunate experience. About a couple of months ago, while i was going to office in train from Brooklyn to Manahattan this happened to me. I was standing along the door and there was gori sitting on the next seat. I was preparing for GRE those days. I was reading some papers at that time so i was looking down on my papers. Suddenly this girl looked at me and this got my attention and i also looked at her at almost the same time.. couple of minutes again this happened and then again. The girl thaught that i am staring at her and she gave me VERY ANGRY LOOK. ........ The situation was embarrasing for me but also i was angry at that lady so i started making funny faces at her and i continued till the end of her journey. But honestly i was feeling quite embarrasing although i had no such intention.