I've written before about key Web features such as degrading gracefully and how that feature is going make the Web a winner on mobiles.
I could be wrong about this, because of widgets.
Widgets are downloaded onto your phone and quite possibly have nothing to do with the original site you retrieved it from on the first place. You could have obtained a widget via a friend or some other arbitrary channel.
So what's the problem? Firstly updating. When you launch the widget, will it be up to date like the Web is? This is not guaranteed as widgets are designed to work offline.
Next problem, features or rather APIs. New APIs like that defined by Opera or BONDI (and later the W3C) are volatile. APIs will change dramatically and they will not necessarily remain backwards compatible.
The Geolocation API changed the position object late 2008. Since it's still not a mature standard, things like this can happen. To access the latitude value, changed from position.latitude to position.coords.latitude. Gears in practice now, implements both interfaces, which can confuse.
What happens when you have a widget that depends on 3 APIs (e.g. file, geo, user interface for soft keys)? On a runtime where 1 of the APIs has been updated? Think of the permutation explosion.
Besides APIs, the new security mechanisms for widgets will also be very likely to be volatile and unstable.
Therefore it will be likely that widgets (at least at first) will be tested and pinned to a particular static snapshot of a widget runtime. As Web developers might simply too lazy to keep up to date.
One solution is that widget runtimes must make every effort possible to keep a widget up to date. Likewise the widget runtime also must be up to date. This is problematic as software updates on mobile platforms have a long history of being ineffective.
Some people might argue that widgets do not have a fixed origin. I would like to argue that someone needs to take responsibility of maintaining a widget on a mobile device.
Perhaps the end user can delegate the maintainership of the widgets on the
device. For example in Debian I could switch my
sources.list from unstable to
stable since I want to use more stable software.
The bottom line is that widgets must be maintained and updated with every advance of the Widget Run Time (WRT).