It's been a known problem publically since June 9th. If I can find the link I'll edit this post.
Additionally (I could be wrong on this) the DAO requires two weeks of voting to correct such flaws.
Two weeks is a recipe for disaster.
It will give somebody trying to exploit flaws enough time to prepare and execute his plans flawlessly.
My thoughts exactly. Without a locking mechanism it seems hard to avoid. I don't think the 20% quorum was going to be hit for some time regardless. Not until a massive consolidation of DAO tokens, would have ruined the whole concept.