I am unsure how any rational technology-minded person could state that they add no value; the idea that a technology which is one of the first Governments try to ban when they are under fire -- that the technology must not be worth anything -- is pretty staggering.
Facebook has a pretty clear path to socially connecting THE ENTIRE WORLD via the Internet, and has proven it can do it in a cashflow-positive way.
I fundamentally don't understand the 'bubble' complaints right now: these companies are the anti-boo.com's of our time: Wildly successful, working, scaling businesses which millions of people rely on every minute to do their work and socializing.
Focusing on valuation for smaller companies also seems silly to me: the YC class that just got $150k per company will be able to punch out some incredibly great and useful technology for that money. In 1999, that money would have purchased 2-5 servers, and no co-location for them. Really. You can worry about a bubble, but if these companies even produce 300k in value, then the investors didn't invest in a bubble, they got their principal back plus a little.
I do think it likely we'll swing back to a slightly less founder-friendly funding regime at some point in the future, but it may also be that we're just at a new plateau given what's currently possible in software. Another shift might change funding dynamics again in our industry; but right now, a whole lot of useful tool can be created for a couple hundred thousand dollars.