Hey Mark - I think you're moving in the right direction by using your blog to start covering some NYC-based startups. You've always had a passion for that.
If a URL shortener goes down - it's likely that all of the enabled URLs go down as well. I don't think we've had a system like that before. If bit.ly went down - half of Twitter would become meaningless.
A DNS or ISP disruption can usually be more localized. I would argue that it's much easier to disrupt a Twitter or a Facebook than it would to take down multiple DNS servers or multiple ISPs. It would take less resrouces and time to create a global disruption by taking down Twitter than it would to take down an ISP.
The point is that a full scale disruption isn't necessary for an impact to be felt around the globe - tr.im is the prime example for that. It doesn't even have to be a malicious change.
It's more about the structure that has evolved - an inverse pyramid of communication vs. the traditional web. At the bottom we have services like Facebook and Twitter with a plethora of applications on top. This adds greater pressure for those foundational services to protect themselves and some have done a better job than other (i.e. Facebook vs. Twitter).
That could work - Yahoo is US, Microsoft is UK (and traditional Western Europe). AT&T could be Italy, Motorola is Eastern Europe. Nokia makes a lot of sense as Japan since they seem to have their own set of priorities but are kinda cooperating with Android (Google)...