I'll leave a note depending on the circumstances.  My fault?  I'm leaving a note.  Their fault? Fuck em.

Example:

I open my door about 3/4 of the way to get out, and just as I take my hand off the door, the wind catches it and it flies fully open into the car next to me.  Fuckkkkk.  I wait about 20 minutes to see if they show, then end up putting my name and number under their windshield to get in touch with me.  Totally my fault, that carelessness was on me.

Example #2:

I go to Genos in philly, anyone who has been there knows parking is a motherfucker.  I park and get out, while I am waiting two new cars replace what was parked in front of me and behind me, leaving me about 3" space in front/behind of my truck.  After I get get back to my truck and see this, I ask all the people there if either are their cars.  I go over to pats and ask there, nothing.  I ask the employees at genos, nothing.  I ask the next two shops down, nothing.  I go over to the park across the street, nothing.  I wait 45 minutes, still no show.  I then proceed to attempt to make a 381 point turn to try to get out of there, it's just not happening.  I wait another 15 minutes and neither shows.  I then proceed to back up into the car behind me and push it back a few feet, impaling my trailer hitch into the front of his car.  As I pull away it takes his front bumper off of his car.  I get out, put the bumper on the sidewalk and then get back into my truck and continue on my day.  Fuck that guy.  He doesnt deserve a note.  There is absolutely no reason to park 3" from someone else, intentionally blocking them in, especially if he has like 5 feet behind him.  Split the fucking distance you inept driver :/