While Google is primarily in the business of running a search engine (and advertising on it), Opera is primarily in the business of selling browsers. But not to you. It is actually in the business of selling browsers to Nokia, and SonyEricsson, and Motorola, and people who make those devices that you hook up to your TV to use the Internet. (Do you know anybody who actually owns one?) Its core competency is making a browser that does a lot of things very well on crappy hardware. So when they get to play around with a full-featured PC, they make the fastest browser on the market, by a good margin. And because on a smartphone, the browser is expected to handle all the Internet stuff, their PC version handles almost everything you could ever want to do online.
Besides being a browser - one with tabs, session saving, a very smart popup blocker, a gizmo that fills in your usernames and passwords on sites you registered for two years ago, and other really useful things - it is also everything else. It is a mail client, albeit one that takes getting used to. It is an RSS reader. It is an IRC client. It's a PDF viewer. The last version is even a BitTorrent client, for heavens' sake! I am not sure why they don't have Trillian-like IM functionality built in, integrating with all the popular networks, but I suspect it is coming soon.
The result is that without making any extra efforts, simply by taking the path of least resistance, the typical user ends up using Opera not as an Internet browser, but as an Internet client! It is not the monstrous Google but the tiny Norwegian that is poised to take control of the Web. Forget about GoogleNet; think instead about OperaNet.
Not that it either will happen, of course. Real life has a way of ending up much more boring than you'd hoped.
I know what you're going to say. You're going to mention Firefox. Don't bother. Firefox is irrelevant in the grand scheme of things because it has a limited potential user base. Unlike Opera, which does everything out of the box, Firefox can be made to do everything by installing a bunch of plugins. Simple users have no idea how to find one, never mind how to install one. Firefox is an alternative browser for the advanced, and its users are the 10% who are unhappy with MSIE. Conversely, Opera's potential customers are the 90% who are perfectly happy with MSIE, and switch to Opera because their twelve-year-old nephew installed it on their PC while visiting over a weekend. It was so simple that they kept using it.