“I’ll wall you” someone teased me the other day. If you do, “I’ll poke you”, I retorted. We both laughed. The person sitting next to us — someone who purports to be “not a geek” — looked mystified. I proceeded to try and explain, that no my friend wasn’t going to come round to my house with a spray paint can and create a personalized urban annotation for me, and no I was not going to reach over with my bony index finger and prod him in the side …