Google is bringing Web apps one step closer to having full desktop functionality. Today, it announced new functionality that allows apps from the Chrome Web Store to run in the background, even when all Chrome windows have been closed but the user hasn't actually exited the browser. Why would you want to do this? A couple of reasons.
There's an example app available here (you'll need Chrome 10).
To close the background apps, users only have to exit Chrome. Users will also be able to check which background apps and extensions are running through the Chrome icon in the system tray in Windows and Linux or the dock on OSX.
To address security concerns, Google has made the functionality available only to Chrome Web Store apps and extensions. Regular websites won't be able to access this functionality. Developers will also have to declare the background capability in their apps.
At the moment this seems only minimally useful, but it does give more purpose to the creation of Chrome Web Store apps, which have been criticized as over-glorified bookmarks.