Microsoft, which introduced Do Not Track in IE9 and turned it on by default in IE 10 and Windows 8, is pushing the envelope on privacy online.
Brendon Lynch, chief privacy officer at Microsoft, said this is a natural progression of a strategy that began when the software first began implementing technology to control cookies over a decade ago.
"People are caring more about privacy as more data is being generated about their activity online," Lynch said. "Privacy is increasingly becoming a feature."
Mozilla uses Do Not Track in Firefox because tracking technology is moving faster than users' ability to understand it, said Alex Fowler, chief privacy officer at Mozilla. "Our No. 1 objective is, how do we mitigate surprise? What things are users not aware of when using features or services?" he said.
When it comes to cookie blocking, Mozilla is trying to find middle ground that accounts for the needs of vendors and end users.
"We're seeing an incredible expansion of money and talent to refine the [tracking] ecosystem, but we're not seeing the same investment in user-facing controls," Fowler said. "We can't just sit back and allow the industry to continue ignoring this core component of users' online experience."
The World Wide Web Consortium (W3C) hasn't yet established a common standard for Do Not Track, and so no enforcement mechanism yet exists.
Google and Facebook aren't crazy about Do Not Track, though Google did add it to Chrome last November, becoming the last major browser maker to do so.
"Until we have an agreed upon standard for what [the Do Not Track] header is going to mean, acknowledging it in some ad hoc way is not going to be consistent with the expectations of users," Google's Enright said during the session.
Facebook uses a social plug-in on various parts of its site, but it's used to personalize content and not for ads. Under Do Not Track, it's unclear if Facebook will be able to continue doing so, according to Egan.
"If we get [Do Not Track], do we not load the plug-in?" she said.
While all four companies were able to cordially examine their differences of opinion during the panel, the complexity of the online privacy debate means it will likely continue inflaming passions for the foreseeable future.
PUBLISHED FEB. 27, 2013