(HTML 5) How much is too much Local Storage?

Some questions considering HTML5 Client开发者_开发百科-Side Storage:

1. How much data in Local Storage is considered too much?
2. Is there a limit on the size?
3. Since its saved on files will it by any means have any effect on the browsers speed?
4. Why use Database storage? is it indexed? Why not use LocalStorage where key is the index (if unique) of the record, and the value is the record JSON stringified?

EDIT

Just a follow up to the Answer, after the WebDatabase project was dropped, all browser are proceeding to implement the soon to be standard " IndexedDB "

Check this other Question. HTML5 localStorage size limit for subdomains

1. It depends on your application.
2. 5 mb is the max size
3. No impact.
4. Database storage is deprecated, so it will not receive more updates. Current browsers support it, yet their implementation may not be standard. So it is not a good idea to use it.