When you translate a website from one language to another using Google Translate, the URL is something like google.com/translate?langpair=en|ar where en|ko is the language pair indicated the site will be converted from English to Arabic.
Now if you make both the languages in the pair same (i.e., en|en for English to English), the translation is effectively skipped but the requested web content is still served from Google servers. Thus, lot of people use Google Translate as a proxy server to access blocked websites.
However, the honeymoon is almost over because Google has stopped accepting website translation requests that have the same language on both sides of the pair (en|en, it|it, etc). Google uses their own language translation software and they have probably done this to prevent misuse of their translation service.
The only consoling part is that this “free proxy” trick still works perfect with other translation tools like Yahoo! and AltaVista Babelfish that are powered by Systran. See a real example that uses Babel Fish – look at the URL in your address bar.