Not so long ago I saw a scientific paper on the effect of false information on learning, which reported the results of an experiment in which subjects who were experts on some subject were given false information about it and then made to take a test. The kicker - the false information was information they knew to be obviously false (say: "appropriate stall recovery in the Q400 involves pulling back on the yoke").
Despite that, though, a statistically significant proportion of them were influenced by the false information. Unfortunately I can't find the study in question, but there are plenty of others in that direction -
you can't really ignore anything,
fake photos change people's memories,
repeating things makes them seem true,
denying things doesn't work very well, and perhaps most importantly,
fatigue helps you form false memories (although coffee helps).