Elizabeth Kasameyer has always loved taking photographs, but only recently did she find a satisfying way to share them: She pays $25 a year to use Flickr - Yahoo's photo-sharing Web site.
By signing up for the online service, Kasameyer joined a revolution that some call "cloud computing" and others have dubbed the "big switch."
With the spread of broadband Internet, Flickr and other Web-based services are becoming increasingly popular. As a result, home and business computing are moving from individual PCs to huge networks owned by companies such as IBM, Google and Yahoo.
Such is the potential for attracting users to Internet-based programs that Microsoft announced a $44.6 billion takeover bid for Yahoo, the second-largest Web portal and Microsoft's best hope for battling Google in the world of cloud computing.
"Microsoft sees that more and more consumer software is going to be served through the Internet," said Nicholas Carr, former executive editor of the Harvard Business Review.
Experts compare Web-based programs to the advent of the electrical grid, which shifted power generation away from individual homes. Just as people now pay for electricity generated from far away, they are increasingly paying for software, data storage and processing strength that are housed on distant computer networks, a combined service that is known as "computing power."
"Some day in the future, you may buy computer power like electricity," said Jimmy Lin, a computer science professor at the University of Maryland, College Park. "It's thinking of things as services as opposed to products."
For many, that future is now. Among the companies challenging Microsoft's dominance in traditional programs, Google now offers Google Docs, a suite of Internet-based applications that compete with classic Microsoft Office programs such as Word, Outlook and Excel.
Experts say the grid approach offers many of the same benefits and drawbacks of the electrical grid. Centralized processing can be more efficient, offering customers more computing power for the buck. But small glitches and security breaches can affect millions at once - and computer automation may cost some people their jobs.
"It's going to continue to make computing much cheaper and available, but will also have ramifications for various aspects of life," said Carr, author of a book on the rise of cloud computing titled The Big Switch.
Whether they realize it or not, many people are already in the "cloud." The most familiar example is the deceptively simple Google search. In fact, these searches harness powerful remote processors and massive databases to troll for fish in a vast sea of information.
Many online services follow Google's model, offering free access and selling advertising to generate revenue. In this manner, Google, Yahoo and Microsoft provide e-mail services and messaging - while social-networking sites such as MySpace and Facebook give users free accounts to help them meet others.
But some companies are also moving to two-tiered models like Flickr's, charging fees for premium online computing services, while offering more basic services free of charge.
Zoho.com, for instance, provides a free suite of Web-based office applications, but charges $5 to $80 per month for additional server space. And Intuit charges monthly fees for online versions of its financial software - $2.99 for its Quicken personal finance program and up to $49.99 for its business accounting program, QuickBooks.
Kasameyer, for one, has been happy to pay for Flickr's premium service. The Johns Hopkins nursing student has made a number of friends through Flickr, and it saved her photos when her laptop crashed. "All my best stuff is backed up somewhere else and not just on my crappy computer here," she said.
But her experiences haven't been all positive. When a church failed to ask permission to use one of her photos in a brochure, she let it ride. But she was less tolerant when a German manufacturer of metal corsets used one of her photos on its Web site. "I had a hell of a time getting them to take down my photography," she said.
Her problems illustrate two major concerns about cloud computing: security and privacy.
Data stored on centralized networks is an appetizing target for hackers, who can reach in from anywhere in the world. Network hubs could also become targets for terrorists or unfriendly countries bent on disabling the nation's technological infrastructure.
Last Friday, IBM announced it was helping a Chinese company to build China's first cloud computing center. IBM said the center will serve other Chinese companies, but experts worry that U.S. technological resources might one day be outsourced to such centers.
"Just like the highway system or water system are important infrastructures, so is this computing grid," said Carr. "It raises questions about national sovereignty that haven't been hashed out."
Carr also warns that centralizing computing power makes it cheap enough that computers could replace humans in certain jobs, shaking up the job market.
Popular online services are already usurping business from more traditional companies that employ far more people. Skype, an Internet calling service popular in Europe, is snatching customers from British Telecom. When eBay purchased Skype in 2005 for about $2 billion, Skype had only 200 employees.
YouTube, the popular video sharing site, also runs mostly on computing power. When Google bought it in 2006 for $l.65 billion, YouTube had only 60 workers.
With the cost of computing power dropping, other professions are likely to feel the pinch. "Any job that requires the interpretation and manipulation of information is a potential target for computer automation," Carr said.
Examples include financial analysts and radiologists who read medical X-rays.
Newspapers have been hit particularly hard by online rivals such as Monster.com and Craigs- list, which siphon away paid classified advertising - adding to pressures that have resulted in staff cuts at many papers.
But there are also hurdles to using large networks of computers to process data and run programs used by hordes of clients.
Last October, Google and IBM gave computer scientists at University of Maryland and five other U.S. universities access to a network of supercomputers, encouraging them to learn how to generate programs that run on multiple machines at once. "When you are normally programming," said professor Lin, "you think, 'I'm going to do this and that and then that.' But when you talking about hundreds of processors, you can't think that way."
Jennifer Golbleck, a computer scientist at College Park, has been using the network to study how members of online social networks decide whom to trust. Experiments that take only a few hours to process on the network provided by Google and IBM would take days on her laptop.
Lin cautioned, however, that Web-based activity still accounts for just a fraction of the market.
"We really want to know if this is a passing fad or if it's good science," he said. "With the buzz and the marketing-speak, it's a little difficult to untangle."