Megan McArdle discusses the unreliability of memory and how this applies to the ongoing suit about subsidies for participants of the federal Obamacare exchanges. But the parts about memory specifically:
People don't remember things that happened a while ago; they remember the stories that they have told themselves about it. I vividly remember sticking a key into an electric socket when I was (I am told) about 18 months old. Do I remember it? Or do I remember being told about it? It feels like a real memory, but all the research indicates that that tells you precisely nothing.
Conversely, I am told that when I was a teenager, a horse reared up and pawed around my ears, miraculously not kicking me in the head. Multiple people agreed that this had happened, but I have no memory of it. Either I've forgotten something I certainly ought to remember -- or they are misremembering something that happened to someone else. No way to tell, because we don't have contemporaneous documentation.
As for Obamacare... we need to go by what's written, not by what people supposedly remember or intended.