Google is hosting popular ajax frameworks/libraries now to speed up the user experience. It makes perfect sense, but I wonder how many popular applications will use it. The package wouldn’t function if the computer is offline.
Let’s say you are working in an offline development environment — you can’t effectively test. I can also see the small possibility that a developer works in a corporate environment where most webpages are blocked. Maybe they blocked everything on google but www.google.com to prevent employees from using gmail, google docs, and google images to share proprietary information. This means the developer has to download the correct version of the framework and change the include line to refer to it locally. The solution is easy, but it could be a real pain to find that bug. Google gears wouldn’t help since the file was never accessible in the first place.
While this seems like a really unlikely case, if you have software that caters to a traditionally strict corporate audience, you’ll either have to offer two packages (local include, Google include) or just go with the local include. The local include is always the safer choice.
There’s also some fine points made on slashdot that this is an excellent way for Google to track ajax usage.