[autoexec]

No, the browser tracks what ads you see/click on, then monitors what you do online for signs the ad was successful, and if it thinks it found one it sends all that data to a third party who compiles a report to deliver to the ad company.

That might be okay to you, but a browser that snoops on my browsing history and reports it to third parties who will then use it to send reports to advertisers is totally unacceptable to me.

[robertlagrant]

It only does that for websites that are funded by advertising. If you avoid those (e.g. HN) you should be fine?

[autoexec]

I mean, if there are no paid ads on the site it won't track any.

That said, I don't expect this to be the end state of their user tracking. They could expand their system to track the kinds of ads we get here on HN too. Maybe eventually start ups will be able to pay Mozilla to track how many firefox users use their web apps after seeing a "Show HN" post or even just after seeing mentions of a product in comments. Right now it's hard to track the success of astroturf campaigns, but when a web browser is working for advertisers instead of being a user agent it becomes possible.