erm... you got me there. I support the theory, but I haven't actually used this technique in any of my projects. You can throw me in the closet and tell me to "practice what you preach"...

But I would use this technique in any Ajax application that uses a permanent data source within a page - for local searching instead of calling the server over and over for a new 'filtered' copy.

AH! Yes I do use this, for several things actually, one of which is an email autocomplete input (an address book lookup)