Most you know Mozilla released Firefox 2.0 the other day. And most you know Google AdSense has a Firefox referral program where you can earn money if someone downloads Firefox. As an FYI - this does not apply to them downloading Firefox version 2.0+, as of now.
A DigitalPoint Forums thread received a response to an email from AdSense support saying;
Thanks for writing in about the Firefox plus Google Toolbar referral button. We currently offer Firefox 1.5 in our referral download. We can't yet say if or when we will offer Firefox 2.0, but I'm happy to pass along your comments to our engineering and product teams.
Forum discussion at DigitalPoint Forums.