Let's take animals and birds for example : 

THEY WILL NOT LET YOU TOUCH THEM TILL THEY ARE CONFIDENT AND COMFORTABLE THAT YOUR INTENTIONS ARE GOOD ..BUT MOST HUMANS WILL TOUCH YOU WITHOUT YOUR CONSENT... SOME DO NOT LIKE TO BE TOUCHED BY STRANGERS BUT FAIL TO STOP AS THE OTHER PERSON WILL TOUCH YOU SUDDENLY OR FAST AND UNEXPECTED SO YOU HAVE NO CHANCE OF MOVING AWAY.

THIS IS EXTREMELY BAD ACTION AND HABIT AS TILL YOU KNOW THE PERSON VERY WELL YOU DONT WANT  TO BE TOUCHED 

EFFECTS : cause you a surprise, unbalance you , make you uncomfortable and also the after effect can last a long time 

KEEP YOUR DISTANCE

AVOID TOUCHING OR LET OTHER PERSON TOUCH YOU TILL YOU REALLY KNOW THEM WELL. 

THE BEST FORM OF GREETINGS IS NAMASTE.

WHICH IS SALUTING THE DIVINITY IN EACH ONES HEART WITHOUT TOUCHING WHICH IS MORE CIVILISED AND POWERFUL AND PLEASENT 

MOST HUMANS NEED TO KEEP THEIR DISTANCE .

A lot of cases of people touching in the tubes and busses mostly knowingly or deliberately so poster had to be put to inform KEEP YOUR DISTANCE 

One cool guy used to go to Hare Krishna temple and hug devotees till he was told off no hugging business but just say greeting like  ..Hari Krishna or Hari Bol.

Most annoying is when people touch you with dirty hands as you should be aware lots don't wash their hands after using the washrooms ...KEEP YOUR DISTANCE AND TRY TO AVOID PEOPLE WHO HAVE A HABIT OF TOUCHING INSTEAD OF PROPER GREETING