I think people are reading this backwards. It isn't just using local storage and indexeddb to protect cookie values from being wiped (by the user), I can see it being more useful for using cookies as an extra store to protect localstorage/indexeddb from being cleared by the browser.
The user can still clear the data manually (clear cookies and other local data) or through a properly written app (which implements a "remove my records from this device" option, and preferably makes the local storage opt-in anyway).
If you are thinking of using this maliciously then you wouldn't use this: you'd use the already existing evercookie instead as it survives more (at the expense of potentially imparting more load on the users browser).
The user can still clear the data manually (clear cookies and other local data) or through a properly written app (which implements a "remove my records from this device" option, and preferably makes the local storage opt-in anyway).
If you are thinking of using this maliciously then you wouldn't use this: you'd use the already existing evercookie instead as it survives more (at the expense of potentially imparting more load on the users browser).