"Rich offline experiences, periodic background syncs, push notifications?functionality that would normally require a native application?are coming to the web. Service workers provide the technical foundation that all these features rely on." - https://developers.google.com/web/fundamentals/primers/service-workers/
For a service worker to be effective it needs to be loaded from the root path of a website, but currently we only allow a few white-listed files to be served from the root, such as robots.txt and favicon.ico.
The ability to serve a single sw.js file from the root path would open the door for developers to start experimenting with this cutting edge feature.
