I think on this one I'll respond that it's probably more a myth, to some degree, than it is real. When you have a smaller system, you are more vulnerable, in large part because most of the time you are on an older version of software. If you have a hundred different e-mails, I can almost assure you that only one is up to date and the other ninety-nine are six generations behind and therefore more vulnerable.
So you would expect, just by virtue of moving to a newer technology, that you would be a lot more secure, because from a security point of view you're up to date on all of the new technology that's available. It would be the same with your data centres and your network. Your data centre sitting in a closet is very vulnerable compared to a secure facility that is running 100% of the time.
So I think there is a little bit of a myth against centralization. There is a physical risk. You have one building or six buildings—the same way the stock exchange is in one building—so there is a physical risk. But from a technological point of view, the risk is actually lower by centralizing.