Maps and terms of use: cache a map?

With spotty bandwidth on a mobile device, it would be great to be able
to cache the map results from google when appropriate, and display from
the cache when there is no internet available.

However, the maps API and terms of use don't explicity deny that
function, but rather hint of that. Combine this with the legal notice
somebody received for tiling google maps into one huge map (for
artistic reasons) and one would really assume the above functionality
is not allowed.

What if my hack really intends to update the cache and never actually
writes to disk?