The worst thing I ever saw was in Burbank, California. For some unfathomable reason I decided to attend a meeting there, walked in early, and the first people I saw were a Gilead couple, home on vacation from their assignment on another continent. I had known them years before they were even married; never expected to see them in CA.
There were about 30 people already in the KH, talking in their little groups. No one even noticed that I had come in, much less greeted me. Worse, the wife of the Gilead couple (a really lovely young woman, always liked her!) was perched on the armrest of an aisle seat completely across the Hall from the locals...alone! No one paid a bit of attention to her! The husband, who had family in that congregation, was likewise alone, standing at the back of the hall.
Of course I went up to the sister immediately and her face lit up when she saw me. She brought me over to her husband and he was glad to see me as well because no one was talking to him either! Remember, these were Gileadites, and wonderful people as well, visiting their "home" congregation!
The sister and I talked right up to the minute the meeting started, and then we sat together. Not a soul in the Hall had spoken to either one of us. Her husband gave a little pep talk during the Service Meeting which was greeted with a yawn.
I didn't stick around too long after the meeting, but during the time that I was there, no one approached me or them, not one single soul.
I am still shocked and this happened a good ten years ago.