1) Two years ago, Girl A breaks up with Guy B to date Guy C. At event, Girl A and Guy C (who have been together over 2 years now, but Guy B still doesn't speak to either of them) have some sort of bad tiff and Girl A decides to avoid Guy C for the duration of the evening. She spontaneously elects to sit and apply facepaint to other event attendees, for something like 3 hours, 5 feet away from the spot where Guy B is stationed whilst volunteering for the event. Guy B's volunteer station cannot be moved, nor can he walk away from this area, where he will be volunteering for a total of 4 hours. Guy B's best friend (female, not me) was first sitting here, also doing facepaint, and is neither friends nor enemies with Girl A, but was also surprised to see her sitting there so long.
2) Go to a Burning Man-affiliated event wearing an exhibitionist garment that's like a bra, but doesn't cover your boobs at all. Then, just in case someone isn't looking at your rack, stick a "hello my name is" tag under your collarbone so the eye is drawn to the boobage.
Now, combine 1) and 2) in one person. One or the other is likely forgiveable (hell, #2 is practically expected), but planting your self and your exposed rack 5 feet away from where your ex (that you had a particularly acrimonous breakup with) is stationed is just classless. I was volunteering where Guy B was and knew the whole story ahead of time, but was still really bewildered at her insensitivity and/or cruelty.
Other than that, I had a fine old time at the event.