For all the fuss over whose Internet platform is bigger, Facebook or Google’s OpenSocial, the biggest platform, and the one that promises the most utility — for social networks, for taking care of business — is the web itself. Full stop.

Speaking on behalf of all of broadband connected humanity, what we want is to be able to carry and access our digital lives wherever we go and from whatever device we may have in hand. That means photos, video, documents, spreadsheets, contacts, and all those various identities we shuttle from site to site. The leading search and social networking sites would have you believe that your digital life can be contained in one place. That’s not likely.

What is far more likely is your digital life will be contained in multiple places and the web will be the hub through which it all flows. If you have a Flickr account, a Gmail account, or are using any web-based application you are already heading in that direction. Your stuff is already in what techies call the “cloud” — also known as the Internet — and not on some local hard drive on your desktop or laptop.

Online storage startup Box.net is among a crop of new firms that see the future in the cloud. The two-year-old Palo Alt0, Calif., company just launched OpenBox, a service that allows other web-based applications access to all the digital stuff you have stored online with Box. OpenBox launched with 10 web-based services, but it’s an open platform, meaning any developer can write an application to hook into the online storage service and let you do a variety of things with the digital treasures you have stored there.

For example, you put photos and images online, you can now edit them with Picnik, collaborate on Word or Excel files using Zoho or fax documents using eFax. Any changes you make are reflected in the source material that is stored with Box. You don’t drag a photo around from service to service, desktop to web. You upload it to the cloud; in this case the Box, once, and then all the web-based services can have at your data.

The key is openness, says Box CEO Aaron Levie. “It doesn’t make sense for us to burden our developers with a proprietary system,” he says. “We want as many users as possible, and the way to do that is to make our service available to as many other services as possible.” To achieve that, Box has a set of its own APIs for developers to use, but is also able to learn the APIs of other services so that Box can interact seamlessly with other systems.

Box is just one example of where computing is headed, into the cloud. Amazon (AMZN), Google (GOOG), Microsoft (MSFT), Yahoo (YHOO), IBM (IBM) and Cisco (CSCO) are among the heavy-hitter technology companies with big efforts underway to put more computing power and more services in the cloud, for consumers and corporations alike. But it is startups like Box that are leading the charge, building new companies and entire business from scratch around the notion that our digital lives will soon be contained and accessed almost entirely via the web. Implicit in that, is the idea that an open system wins and the only platform that really matters going forward is the web.