Sign of Age.

You know you are getting old when you are irritated by letters from "Nick" at the bank. In Germany, you would scrupulously observe the "du" and "Sie" forms of "you". Never, I was taught, move from "Sie" to "du" without explicit permission — it could take many years, and might never happen. I still sign "yours faithfully".

So, while being the grumpy old man, I would add:

• Chewing gum. (A research topic: plot the abundance with distance from an exit of Oxford Road tube station - not exponential, but a power law I suspect). The plaza of the British Library resists heroically!
  
• Feet on seats. Default behaviour if you are under 30. Place the sole on the edge to effect maximum transfer of dirt.
  
• Street sweeping behemoths, shimmering with exhaust heat, usually on crowded pavements. Totally disproportionate solution to a problem.
• Gas heating outdoors on pavement cafés and in pub gardens. Literally burning money, even if you don't believe in global warming.

It arises, I let it go — most some times!