Recently, I was at a seminar in one of the midtown hotels. You know, a few hundred people in neat rows of seats behind narrow tables. Since this was a high-end seminar, coffee was served. I took a cup back to my seat and placed it on the table in front of me.
No sooner had I done so when a women - seeking to find a seat in the row in front of me - went down the row and, with her bag, knocked over my cup,spilling its contents over my presentation materials. She didn't have a clue as to what she had done. My spontaneous exclamation was either not noticed or purposefully ignored.
This is not the first time that “baggage” carried on persons (more often on women but also on men) has caused calamity. A particular annoyance is being hit in the head while sitting in a theatre by the handbag of someone walking down the row behind you. Many, many near misses - avoided only through extreme diligence or, frankly, good luck. Notwithstanding reliance on luck, I have taken to be extremely protective of things on tables in restaurants when a neighbor must slide out between tables.

Bags, backpacks, and other physical extensions of one’s person. Know your boundaries.