On my RS, just a couple years into ownership, doing my 4th or 5th ever oil change, once I was done, I started her up and checked for leaks. Oil was pouring down around the oil filter. Stopped the car, pulled the filter, and found the o-ring from the previous filter didn't come off with the old filter.
Worst part about this? My brother, also with an RS, did the exact same thing just a week or two before, and when I was getting ready to change mine, warned me to check that the o-ring came off.