>Yes, storing data permanently on the client is generally a bad idea. However, storing temporary (cached) data such as lookups for increased speed; storing data locally while disconnected, and storing data locally for buffered cursor manipulation are at least three use cases for local storage that I can think of right of the bat. Hit the server as little as possible -- only when you need additional data or when you are ready to commit changes.

it's never easy for me to switch from a development paradigm to another ...
FoxInCloud leaves all data manipulation on server, client only deals with presentation via HTML & AJAX, never loads or sends raw datasets ...
- lookups : AJAX incremental search / autocomplete limits data to retrieve
- disconnected : why not, though requires moving some part of business logic on the client
- buffered cursor : FoxInCloud does that on the server