The ostensibly pro-consumer "Do Not Track" specification under development now mandates that it be an "opt-in" feature. Ryan Singel at Ars Technica:
The latest proposed draft of the Do Not Track specification published Wednesday requires that users must choose to turn on the anti-behavioral tracking feature in their browsers and software. That means that Microsoft IE 10, which the company announced last week will have Do Not Track turned on by default, won't be compliant with the official spec. Which means that tech and ad companies who say they comply with Do Not Track could simply ignore the flag set by IE 10 and track those who use that browser.
Most browser makers have big stakes in the advertising business: Google makes its money from ads, Microsoft is serious about Bing, and Mozilla is financed by search engine affiliate cash (i.e. Google and Bing). Wouldn't it be something if Apple ended up seen as web privacy advocates, simply because their bet is on apps and they have much to gain at others' expense by marketing privacy as a desirable consumer product? Unless I'm very much mistaken, and forgive me if I am, Safari is already the only browser to block third-party cookies by default.