Ok, here's a couple of the studies I was talking about:
Elizabeth Loftus and Jacquie Pickrell from the University of Washington in Seattle: 120 subjects were shown pictures of visitors to Disneyland meeting Bugs Bunny. Over one third of the subjects interviewed said that they knew that they had indeed met Bugs Bunny when THEY went to Disneyland. The only problem is that Bugs is a Warner Bros. character, not a Disney character, and as such never appeared in any Disney parks.
Another study showed that people remembered drinking a certain type of soda out of a glass bottle in their childhood, even though the glass bottle had only been in production for ten years! Before that time it only came from fountains.
Of course, memory is incredibly faulty anyway! In a study at Kent State University, a stranger would stop a student and ask for directions. Part way through, two men carrying a door would walk between them, momentarily obscuring their view. They would finish their conversation, and then were asked if they noticed any change happen. Over half the students failed to notice that the person they started talking to wasn't the same as the person they finished talking to! They were switched when the door passed by. They failed to notice that the build, hair style and color, clothings style, and even voice was different!
As Lynne has mentioned, you can focus so much on one thing that you see it even if it isn't there. The reverse is true also: in one study subjects were asked to watch a clip from a basketball game. They were further asked to count the number of times the ball was passed by one team. At the end, they were asked how many passes there were, and if they noticed anything odd in the video. Around half failed to notice a woman in a gorilla suit walk slowly across the scene, even though she passed between players! When shown the video again, many even refused to believe it was the same tape, thinking it had been switched as a joke...
Memory is fragile, and even among large numbers of collaborating witnesses a "true" picture can't always be obtained. Nobody sees everything that happens in a scene, and often we miss the gorillas... Now, if she hadn't been wearing anything, I bet I would have noticed!