Google originally pioneered Gears as a way to get webapps to work offline (at a time when HTML5 was still being hashed out by WHATWG) and tried to get it adopted as an open standard (http://gearsblog.blogspot.co.uk/2008/04/gears-and-standards....).

Spreadsheets had (view-only) offline capability via Gears as far back as 2008 (see http://googledocs.blogspot.co.uk/2008/04/view-your-presentat...) but this was then discontinued in favour of the standards methods. FWIW, they have been helping with the HTML5 storage APIs from the beginning.

The HTML5 way of doing offline is AppCache, which Google have used for other products (http://googlecode.blogspot.co.uk/2009/04/gmail-for-mobile-ht...) and are presumably using here (or the alternative FileSystem API - http://dev.w3.org/2009/dap/file-system/pub/FileSystem/).

I suspect the Chrome-only limitation is due to the differences in the way is currently implemented, for instance:

* Until Firefox 26's release yesterday, it would prompt for each site that wanted to use AppCache (https://news.ycombinator.com/item?id=6881368).

* Firefox doesn't handle the no-store directive well

* Chrome Apps can be granted unlimited storage (https://developers.google.com/chrome/whitepapers/storage#unl...)

If it worked in Chrome outside of the store, it would be more plausible. But requiring the Chrome Store seems to indicate it is not using just standard HTML5 stuff like appCache. The issue of limited storage or not seems insufficient to explain this.

Very disappointing.

With DART and Go and Google Fiber, all one company. It kind of worries me to be honest. Overall though as long as Larry and Sergei are there it should be OK I think.