The data wouldn't need to be guaranteed to live forever, especially for applications like simple multiplayer games. Also, the client wouldn't need to depend too much on a particular benevolent server, since the server could be open source, and anyone who wants to run a server could do so, like Etherpad.
update: It may also be possible to include a simple login system. This would allow read/write access rules. For instance, someone could create a survey, and allow clients to submit data, but not allow clients to read the submitted data of other people (only a certain user could read that.. whichever user it was that setup that particular "bin").
This would also allow a strange mechanism whereby a user "runs a server on their own machine" which is really just a webpage logged in as a certain user which access to periodically update various bins according to certain "server logic".