The masses are switching to Chrome for several reasons, most of which have to do with "it's more cool," whatever that means. They don't care about the tech or the JavaScript performance or the memory usage or even the extensions. And they certainly don't care if the browser tells them to upgrade, if all that means is pressing a button and allowing it to restart in a couple of minutes. Most of all, they don't love OR hate Chrome, they just like it. And the new UI and frequent upgrade cycle are nothing more than Mozilla trying to keep up with Chrome. The masses were already leaving.
Mozilla's problem is that their core constituency is passionate about their browsers. Without geeks who care deeply about technology (open standards, in particular,) Mozilla wouldn't even exist. Now, they are trying to please their core while maintaining mainstream appeal. The problem is, the other browsers, including IE 9 (which I still hate,) are doing the tech piece just about as well. In some ways, they have done their job too well. They raised the bar (with the support of their core,) and M$ and Google have responded. Mozilla is trying to please everyone, and we know how that goes. My vote: stop changing the UI, focus on the technology, standards support, and flexibility, and forget about market share.