I looked at doing it but you run into a few architectural issues. Keeping the database updated would still take a connection to the net (as its not viable through iTunes). Storage wise you are probably OK, but if you look at a well designed web app that can keep the information in the cloud, and as long as you have a good connection (3G or WIFI) then its probably the better way to go. It can become a collaborative effort to keep the data up to date and you are always looking at the most up-to-date data via the web.