I'm with Acidus on this one.. This is more of a gift to people looking to do evil things to people, than it is to creating interesting websites. There are way better ways to handle shared storage between websites.
In this post I'll walk through some of the ways web application developers take advantage of local storage to speed up applications, persist user preferences, and enable features for "occasionally connected" users.
A web application can rely on local storage options when disconnected from the Internet, saving changes locally and synchronizing results whenever an active Internet connection is available.
Imagine a personal finance site storing your stock portfolio and historical prices locally, creating quick access to charting and planning tools powered by pre-loaded data.
I swear on all that is holy Niall Kennedy, for even suggesting this, I am going to punch you in the face if I ever meet you.
Current versions of Firefox 2 allow unlimited storage through the DOM Storage feature but future Firefox releases (post-2.0.0.1) will restrict usage to 5 MB per-domain. A website can access not only data within its own subdomain or domain, but within a given top-level domain (.gov, .com, etc.) or any requesting page, creating some interesting opportunities for shared data namespaces.
Why is it every time I turn my back the web developers of this world decide to collectively binge drink on stupid?