"Ummm…" is the new “Excuse me.”

Always out of the loop, I was not notified when this change was declared. There was a time when people came up to you and addressed you, saying something like “excuse me,” or “hey, dummy.” You know, something that acknowledged your existence. Increasingly, people of a variety of ages, but definitely on the younger end of the scale—twenties and below—stand nearby and say ummmmmmm, sometimes several times, until they are acknowledged. They even do this when I am talking to another patron. I try to ignore them until they actually say a word or two, preferably in English, but I'm not that picky truth be told. 

This goes along with an earlier change. When someone performs a service for you (let‘s say answers a reference question as a completely random example) you no longer have to say “Thank you.“ It is now sufficient to say, “OK” and walk away.