The internet interprets censorship as damage and routes around it.
DNS is the deliberately centralized part of the Internet. Big sites that host user content (Youtube, Facebook, Twitter, Blogger.com) are a very large and very centralized part of the Web. Both are located more or less entirely in the US, and both are the explicit targets of SOPA. Furthermore, existing laws like DMCA have caused a lot of damage but have not been effectively circumvented or routed around.
Edit (thanks Wedfrid): please provide stronger evidence to support your prediction that SOPA will be routed around. The best proof would of course be a description of how to do it, but that may not be conveniently available. However, merely pointing out that there are some very smart people opposed to it is very weak evidence.
There are possible technological solutions to the problem of decentralizing the Internet. None of them are immune to their authors and redistributors being arrested or C&Dd, both in the US and in allied countries, under laws that prohibit "tools that aid copyright violations".
There aren't any publicly known technological solutions to the problem of decentralizing the Web, because people who don't understand or care about technology politics will not agree to leave Facebook et al.
My prediction that such crap will get routed around is more of a "water rolls down hill" sort of thing.
Even so, here is my take on how DNS blocking will go down: there are many, many, many projects and possibilities for decentralizing and fortifying the internet. Namecoin has been mentioned, I don't know if .p2p is the same as namecoin, but it's similar idea. .onion isn't going anywhere, because civilian use of tor provides cover for military use of tor. I myself have dabbled in designing kademlia-like decentralized overlay networks that don't re...
Referring, of course, to the proposed U.S. legislation which could cause severe damage to the Internet—at least, that's what a lot of people are saying. See, e.g., this Open Letter From Internet Engineers to the U.S. Congress (the first signatory listed is Vint Cerf). On Wikipedia, people including Jimbo Wales are discussing strategies as extreme as blanking the entire site (except for an explanatory message) to get people's attention, and thereby perhaps incite them to action, such as calling their Congressional representative.
I just happened to find out about all this a few hours ago, being someone who tries to avoid distractions like most kinds of news, so possibly others here with similar habits will appreciate having it called to ther attention. Or possibly they won't. But to those of you who possess relevant kinds of expertise:
(I think this subject can be discussed without political advocacy, in which I am mostly not at all interested anyway. It just looks like a practical problem to me.)
Edited to Add: I forgot to include a fourth bullet point:
It seems to have been assumed by many commenters, nevertheless.