Are DuckDuckGo redirects a privacy issue

Author's note (July 2016): The answer below was written in 2011, and is still working in Google Search. I have published new extensions that use a different method to remove the search result indirection, which works on even more Google sites and on mobile.

TL;DR: _{^{Don't track me Google is a user script}} Don't track me Google is an extension I made that allows you to copy normal URLs, while hiding the referrer to the sites you're visiting.

Installation

• "Don't track me Google" at the Chrome Web Store (updated in 2016).
• "Don't track me Google" for Firefox (desktop & Android) (since 2016).
• "Don't track me Google" at Userscripts.org (works in Google search only, not updated any more)

Explanation

I have written a method which replaces the link-modifying rwt function with a bogus function that can't be touched by Google.

By preventing Google from overwriting the rwt function, the link cannot be modified any more. This method depends on the Object.defineProperty method (Firefox 4+ and Chrome 5+). The fallback requires Firefox 2+ and Chrome 1+.

Firefox 2+

If you only want to remove the link-modifying behaviour, and not care about showing your search queries through the referrer, this GreaseMonkey script can be used:
(very non-strict @include rules using wildcards and the Magic TLD)

// ==UserScript==
// @name           Don't track me Google
// @namespace      Rob W
// @include        http://*.google.tld/*
// @include        https://*.google.tld/*
// @version        1.2
// @grant          none
// ==/UserScript==

"use strict";
if (Object.defineProperty) {
   Object.defineProperty(unsafeWindow,"rwt", {value: function(){return !0;}, writable: false });
} else {
   unsafeWindow.__defineGetter__('rwt',function(){return function(){return !0}});
}

Google Chrome does not support Magic TLDs, so the closest you can get is *://*.google.com/* (repeat the rule, replace .com with other supported Google TLDs).

In Chrome, scripts have to be injected in the form of a <script> tag, because Content scripts are executed in an "isolated world".

Chrome & Firefox 2+ - Link to source code

On January 21st, 2012, I published an extended version, which includes a referrer-hiding method, so that others cannot see your search query. This greatly improves your privacy.

• The mechanism is explained at this answer on Stack Overflow.
• Additional details are available at the source code and Don't track me Google description, a user script which fixes the URIs and hides the referrer.

(Update from 2016: this referrer hiding is not needed any more in modern browser because of the referrer policy, which only shows the domain in the Referer header)

The redirect from the regular start page states:

Clear your cookies often? Try our homepage that never shows these messages: start.duckduckgo.com

...this implies that the regular homepage sets a cookie to hide messages the next time you visit, while the "start" page just never displays them.

According to an official DDG support representative on the DDG forum, start.duckduckgo.com was introduced in 2016 as a "cleaner start page". You'll notice there are fewer UI elements, such as tips or links to add-ons, at the start.duckduckgo.com domain. The search experience is exactly the same, though.