I started filling out my hosts file with my most common sites a while ago...just in case.
If it does happen where everything is based on an IP, the web, ecommerce, all of it, will die. You can't advertise a business as an IP address. In a couple days millions won't be able to find any websites anywhere.
Ad revenue will be GONE, nobody will be paying for ANYTHING online and every one of the sites you've written down will surely close their doors because there is no way for them to stay in business.
Small businesses everywhere will fail. Websites like Reddit, HN, Digg, etc, will not be able to survive.
Google will become useless. Since their search results can only return a handful of sites, you might as well go right to them, bypass Google.
Hosting companies will fail left and right as their sites are slowly shut down and their customers leave. There won't even be anywhere to keep websites online anymore, IP or not.
And so on.
I think the people of the USA should be happy there needs to be a law around it at least. Here it was blocked with no legislative backing, only because a judge deemed it illegal. It's interesting to see you at least have a semblance of democratic process.
Personally I think it's only a matter of time until there's a "hacker" DNS servers for people to completely bypass all this shit.