The Fragile Internet
vukicevic.blogspot.com
The new Internet is based on a set of principles that depend on susceptible bottlenecks such as Twitter and Facebook. Disruptions to these bottlenecks would have global ramifications.
vukicevic.blogspot.com
The scale of attack that is required to completely bring down any of the large services that we use on a daily basis are so large that they could otherwise be focused on the DNS infrastructure, or the internet infrastructure of a decent-sized country. Much smaller attacks have been used in the past to take out large IRC networks (hence disrupting communications for hundreds of thousands of users). Mail bombs, spam attacks on news groups, internet worms, etc etc. This has all been going on for years. If anything, companies like Facebook and Google are better equipped to deal with the threat than most, because they have the resources to do so as a high profile target (note that I don't include Twitter in this category, because they have had trouble staying up under normal loads).
So I don't think this highlights the fragility of "the new internet", it's just the fragility of the internet in general. An attack on the scale required to take down Facebook would be able to cause similar amounts of disruption almost anywhere it was targeted.
If anything, I think the rise of rapid provision of cloud computing resources are probably making the internet _less_ fragile, in that a well-designed application can scale proportionally to its (legitimate) user base within hours or days, not weeks or months as it used to be.
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).
And how do additional layers create more fragility, when the most fundamental layers (e.g. ISP infrastructure, DNS) are just as vulnerable to attack as the application frameworks implemented on top of them?
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.
An infrastructure disruption at a large colocation provider would probably cause just as much inconvenience to users. Attacks against root name servers can (and have) cause huge amounts of disruption.
I understand your point is about people building upon single points of failure, but my point is that there have always been single points of failure within the internet. I don't think conceptualising facebook as a single point of failure is particularly accurate either, given the distributed nature of its implementation. You're more likely to get localised failures of facebook than a complete outage, which would appear to be exactly the same amount of risk as any other situation which I've described.
As for URL shorteners, it seems apparent that there might be a business opportunity in client-side hashing with a server-side implementation for those without client support. That way you remove the point of failure, which I agree is a good thing, even if we disagree about how important that point of failure is.
Facebook might not be a perfect example - I think Twitter is probably better since it's more of a platform.