Tim O'Reilly has written another great essay explaining the three types of cloud computing: Utility Computing, Platform as a Service, and cloud-based end-user applications.
For now let's focus on just one consequence: "Web Services" finally get real. Let's go through the various services that are already emerging. Remember, these are not only services for consumers, but also a platform for developers.
Most obviously, identity. This includes authorisation, authentication, presence, and basic user data e.g. email address. OpenID and OAuth are the emerging standards in this space, with support already from Google, MySpace, Microsoft, and Yahoo.
Secondly, social networking basics : Friends & the Activity Stream. OpenSocial is the emerging standard here.
Third, basic content: Images, Videos, Audio, Blogs. The emerging standard here is Atom. However services will likely get enhancements; for example, the ability to manipulate the underlying files e.g. removing red-eye on photos or enhancing audio treble.
Fourth, various additional services:
- Location-based services e.g. Maps / GPS
- Time-based services e.g. calendars / tasklists / clocks
- Messaging (email, instant messaging, phone)
- Financial services (payments, credit checking, etc)
Finally, professional content:
All of these services already exist on the web, but they are in silos and can't easily be accessed by developers. Finally now, web application providers are rushing to become platforms for developers, opening up their data using standard patterns like REST and OAuth.
For example, Paypal could offer to track your payments in Google Calendar. Or you could ask the BBC to enter any news items within 20 miles of your house into your Myspace Activity stream. Or you could put your phonecall history there. Or your project management system at work could put events into your personal calendar or task list.
From the consumer perspective, the web will become a lot more connected and personalised. From the developer perspective, there will be a huge number of web services making user data available securely (photos, videos, friend list). Writing a web application will involve plugging in to these standard services. Finally, the vision of web services will become real.