I know someone who's full name is too long for a ticket but fits on the passport. He called the airline who said it was ok to abbreviate it. And it was.
Another time an agent booked a flight for me and the last name was wrong. I called to ask if it could be changed quickly and the answer was just go anyway, nobody will notice. He was right. I went through at least four controls and nobody noticed the difference.
Quite recently there was also a discussion between some passengers just after boarding. The FA discovered that two pairs of passengers had the same seat numbers but two of them were supposed to be flying to another destination. The ticket check at the gate was obviously not so effective.