Like other perimeter security systems, it's vulnerable once someone gets behind it. This is not as clear in the other terms being used. I'm personally very concerned that a lot of organizations are preparing to deploy VNPs and are not making sure that all the member sites of the VNP recognize that a common security perimeter is being built. This is flawed thinking and marketing hype. I don't think they particularly care about the packet formats or any of that, they just want to make sure that their patented technologies are used for key exchange.
Standards are only relevant if they're timely.
Won't stop the major vendor wonks from trying to push proprietary stuff as standard regardless of what the network is trying to accomplish using open protocols openly arrived at through discussions such as this, though. I think disagree with the meaning of the terms as Marcus presents them here. I disagree with his statement that VNPs are what are really being built. They are, and should be, different. Both are useful.