They are like putting the condom halfway on. Why in God's name would anyone do this? The reason oral operating agreements make no sense is that when they are violated it's very, very difficult for the wronged party to prevail. Remember that the plaintiff has the burden of proof in American civil cases. So when you sue the other LLC member for breach of an oral operating agreement, it is your word against his. Without some additional evidence such as course of dealing or emails / correspondence from the defendant acknowledging the terms of the oral agreement, the plaintiff loses for failing to carry his burden of proof.
Are oral operating agreements enforceable at all? To my knowledge, other than in the District of Columbia, oral operating agreements are enforceable; however, certain terms such as the agreement to make capital contributions must be in writing depending on the state. See state survey of LLC law.