Whether you send the data to the client as a hidden field in a form, or as a cookie it's basically the same thing. And by using a cookie you can be sure that the data will be in every request the user sends (GET's, links, images, media, etc) from then on, not just the results of a form.
in reply to Eliminate server-side state to obviate cookies
in thread "omniscient debugging" for Perl
While this would reduce the need for server side storage of sessions, this can already be done. There are lots of people who instead of sending a session id in the cookie (or hidden field) will send a serialized version of an object or hash which they can then unserialize at the next request.
-- More people are killed every year by pigs than by sharks, which shows you how good we are at evaluating risk. -- Bruce Schneier