Some of my MUP observations:
Slower cyclists with mirrors that don't know enough to stay to the right...also never look in their mirrors.
Saying "on your left" produces some strange reactions...
a couple of days ago I was passing an older couple on bikes on when I called out, the woman began ringing her bell for some reason.
One time an older man swerved his bike to the right when I called out right into his wife. They both crashed.
Last week I called out to a doofus cell phone talking/dog walking guy who was weaving from one side of the trail to another. He fliched and crouched to the side of the trail and shouted into the phone..."Holy Christ they're all over the place".
If there is room to pass without calling out I will pass silently.