In practical terms, this means that Man-In-the-Middle BGP route hijacking has now moved from a theoretical concern to something that happens fairly regularly, and the potential for traffic interception is very real. Everyone on the Internet — certainly the largest global carriers, certainly any bank or credit card processing company or government agency — should now be monitoring the global routing of their advertised IP prefixes.
This kind of attack should not happen. You cannot carry out this kind of hijacking without leaving permanent, visible footprints in global routing that point right back to the point of interception. We believe that people are still attempting this because they believe (correctly, in most cases) that nobody is looking.