Ask HN: Safety Critical infrastructure on the Internet

I've been following the Protecting Cyberspace as a National Asset Act of 2010 and while I understand that the "President pulls the plug on the internet" stories are a little exaggerated, it got me thinking about what truly important systems rely on the internet.

Easy ones that come to mind are: Email communication Phoneline back hauls Stock market electronic trades Cost aware thermostats (imagine they all loose connectivity, default to max usage and bring the power grid down)

What other safety critical infrastructures rely on the internet?