There is already a Firefox extension called DeSopa for DNS evasion that says it would bypass SOPA tracking if it ever came to pass (we hope not).
When turned on, DeSopa intercepts URLs, sends the base URL to three offshore DNS services via HTTP, makes a best effort to check that two of them are equivalent, caches the IP for the browser session, redirects to the equivalent URL using the IP, and substitutes out the domain name in the source code with the IP address for future requests.
The add-on has been preliminarily reviewed by Mozilla. It was launched under the GNU General Public License on December 19th. The add-on was developed by T Rizk of Cambridge, MA, who lists http://www.inficron.com/ as his homepage.