The other day a teacher added me to FB. It's strange, but I liked it. I remember years ago one specific class I had with him. We were seeing quantum computers (extracurricular). That's when I asked something simple like "why does Fermi has to be right?" Why does the Pauli Exclusion Principle holds true? The answer to that doesn't matter, just his answer. "Well Mr. Computerist [the name he used to refer to me], just believe it as right. It's dogma. The same way you believe in the virgin Mary." To which I replied, "Sorry, I'm not in that business. I'm atheist." To which he remained silent.
I think I got his respect for that answer. In my imagination that's why he sent me the invitation. I can see teachers turning students to a faceless sea of people "learning". He remembers me :p

Update: I see that he now has more students... c'est la vie.