W3C Storage has a few exception behaviors this abstraction doesn't handle and thus might be something to worry about:
* setItem(key, value) can throw a QuotaExceededError.
* Any of the Local Storage methods can throw a SecurityError. I have in my notes that Chrome does this when a user disables cookies.
There's a second problem: this thing is synchronous, so it's not possible to create a backend for WebSQL, IndexedDB or remote storage, or to store stuff in (possibly shared) WebWorkers.