Wikipedia: http://en.wikipedia.org/wiki/Posthypnotic_amnesia

"memory wiping" might not be the best term for it, since the memory is still in there, just really hard to access, but it's definitely a real effect.

I've also personally used hypnosis to achieve the effects on friends of mine (who I'm certain weren't just pretending), as well as to many strangers on omegle (who could have been pretending, but based on what I know about hypnosis I doubt they were).