Many Web 2.0 applications are incredibly small and tightly focused. Some do one thing and one thing only, like the Notify Me When It Is Up application, which, no kidding, will notify you when someother application — like Gmail or Twitter — is up and running again.

While NMWIIU is a bit of a joke, it demonstrates the way that many Web 2.0 applications are focused on doing one thing, and that one thing simply.

Simplicity has been getting lost in the Windows Office Suite generation of products, or the ’90s generation of enterprise software, like Lotus Notes, where the user experience was always like trying to eat a meal with a Swiss Army knife. Sure, you managed to get the food in your mouth, but the knife made it more difficult than necessary.

The tight focus of the best Web 2.0 applications — like Twitter, Get Satisfaction, and Harvest — makes them easy to grasp and quick to be useful.

Twitter is a very well-known phenomenon these days, and it is making major inroads, including becoming an adjunct to television shows. But at core, the application is simple, doing only a few things.

Likewise, Get Satisfaction is ‘people powered customer service’ where users questions or recommendations about products are published, and the corresponding companies can ‘claim’ their accounts and answer the questions. A very simple dynamic, made tightly focused by the application. Instead of learning 20 different customer support systems, I can simply gripe at Get Satisfaction about all the products I would like to work better.

Harvest is a relatively simple accounting solution, focused on cash management, like timesheets and invoicing. It is several orders of magnitude less complex than Quickbooks, and the learning curve is incredibly short: because it does not try to do everything, but only the critical 20%.

As I will explore in later posts here, by making tools small and focused — but open — we are starting to see the growth of Unix-like aggregations of tools, confirming Tim O’Reilly’s vision of the Web as a platform, as an operating system. More to follow.