Internet vulnerabilities

There is a lot of news lately about terrorist groups doing recon on potential targets. The stories got me thinking. What are the real threats to the global Internet? I am looking for anything that might be a potential attack point. I don't want to start a flame war, but any interesting or even way out there idea is welcome. Is it feasible that a coordinated attack could shutdown the entire net? I am not talking DDoS. What if someone actually had the skills to disrupt BGP on a widescale? jas