Earlier today, Microsoft accused Google of manipulating Internet Explorer's default privacy restrictions in order to "bypass user preferences about cookies." Google's just responded with a lengthy rebuttal, arguing that Microsoft's P3P cookie technology is "widely non-operational," and that the issue has been around since 2002. The response also points to other offenders, citing a 2010 Carnegie Mellon research paper that says over 11,000 websites don't use valid P3P policies.
Google's also specifically bringing Facebook and Amazon into the fracas, citing their similar use of the P3P bypass. Google references Facebook's policy on P3P cookies, and says that it and other websites have been open about their approach. Both Facebook and Google say that P3P doesn't support their modern web services — Google says that "newer cookie-based features are broken by the Microsoft implementation in IE," and Facebook's policy states that "the P3P standard is now out of date and does not reflect technologies that are currently in use on the web."
Here's an excerpt from Google's statement:
Microsoft omitted important information from its blog post today.
Microsoft uses a "self-declaration" protocol (known as "P3P") dating from 2002 under which Microsoft asks websites to represent their privacy practices in machine-readable form. It is well known - including by Microsoft - that it is impractical to comply with Microsoft’s request while providing modern web functionality. We have been open about our approach, as have many other websites.
Today the Microsoft policy is widely non-operational. A 2010 research report indicated that over 11,000 websites were not issuing valid P3P policies as requested by Microsoft...