Earlier quoted context omitted.
Other issues: * It's leaking a lot of information (Google Analytics and a few other domains are being connected to directly instead of going through proxy). This is probably the biggest thing to fix. Offering a "strip all scripts" option may help. * Useragent is set to Go's default. Forwarding the user's user-agent or better yet, a stock browser useragent (Firefox or something) may be better
That first issue isn't really generally fixable, is it? At least, not for a web-based proxy like this. SOME effort could be made to rewrite URLs found inside of Javascript but that might be a terrible idea in practice.
If you're allowing Javascript then it'd be tough but if scripting is stripped it should be doable.
For anonymizing, stripping Javascript, Flash/plugin content would be essential I think.