woh! weird analagies coming into play now
i am just happy that wikipedia is available offline.
but of course, it would be the icing on the proverbial cake to have maps offline i agree, size issue would come into play as mentioned. the wikipedia alone is 2GB, and that is just textual information. think of the binary data and associated files needed for maps!
maybe when we are a few gens into the iphone with bigger storage it would be viable, but i am sure GPS will kick in before that is possible. so 'offline' may become an un-needed way of obtaining mapping.
i would definitely pay for it also, like a commercial one off fee or license, as i only have wi-fi in the house, no data plan or on the go data reception.
good luck with the request and hope it comes to fruition down the line...