Memoir is written from how the author remembers something. It is a VERY flexible medium in that way. And a lot of good writers, I think, are ones who have a sort of casual relationship with truth. An embelishment here, a creative lisence there... we'll never really know where the line is blurred. Outright frauds should still be found out and exposed, but the nature of memoir itself is often to blur the line between reality and fantasy.