Well, it sure looks like IBM is keeping all its supercomputing bases covered these days, with it not only working on a chip-sized supercomputer, but a global-scale shared computer that'd be capable of "hosting the entire internet as an application." That latter word comes in the form of a white paper ambitiously dubbed "Project Kittyhawk" (we're guessing they found "Project Mulitvac" a little too obvious), which aims to explore the construction and implications of such a massive scale computer. That apparently wouldn't be a SETI or Folding@home
-style shared computer consisting of everyday PCs, however, with it instead relying on IBM's petaflopping Blue Gene/P
as a common platform, which would effectively be able to run any web-scale application you could throw at it. Of course, none of that has moved very far beyond the page just yet, so you can rest easy that there's still no supercomputer out there that's capable of bringing the entire internet to the halt on a whim, at least that we know of.