Each of Google's technologies is another step in transforming the role of the desktop browser. In Google's vision, the browser isn't merely a thin client for displaying Web content; it's an active participant in the Web applications ecosystem, sharing UI, storage, and even data-processing chores with the server. We're already at Web 2.5 and counting.
Mobile browsers can't keep up
That's great if you're designing Web applications for the desktop, but mobile is still largely a Web 1.0 world. Compared to a modern desktop browser like Chrome, today's smartphone browsers are feeble toys. They're getting better, but the idea that you could have the same Web experience on a handset as on the desktop is still a pipe dream.
Take HTML rendering, just for starters. Handset screen sizes are still a problem, but modern Web standards have made coding for diverse form factors much easier -- if the browser follows the standards, that is. Good luck finding one that does! According to Peter-Paul Koch, even browsers that implement WebKit have varying degrees of standards compliance -- enough so that Koch claims "there is no WebKit on mobile." And what about the handsets that don't implement WebKit?
Gears technology is available on Google's Android OS, but good luck finding it on other smartphones. And Native Client technology is completely out of the question; it relies on properties of the x86 architecture for its security model, so it can't be ported to any current handset.
Can developers support two Webs?
In short, while the Web experience on the desktop is undergoing a technological transformation -- scaling out as it scales up -- the mobile browsing experience isn't much better than how desktop browsing was a decade ago. The more that modern Web applications take advantage of the new client-side technologies available in desktop browsers, the more the divide between the desktop Web and the mobile Web widens.