I have no problem with the Fredo opened the drapes theory. Up until yesterday, I was a firm believer. Once I saw the blurb on the bonus disc though, I couldn't help but be swayed a little. It just doesn't make any sense why the movie makers would tell us what Fredo did to betray Michael and mention nothing about the drapes in their explanation. Since we're discussing a fictional movie, there are always going to be plot holes, but the omission of opening the drapes in the explanation doesn't fall into that category. In trying to keep the audience guessing as to who the traitor was, FFC had to use as little detail as possible, hence the unanswered question of who opened the drapes. In explaining Fredo's betrayal after the fact, there was no such need for suspense, just a straight forward explanation, which is in fact given, but includes no mention of opening the drapes. Just when I thought I was out of the drapes discussion, the family tree pulls me back in!