As far as I can tell, you are not supposed to store any Geocoded data from Google into a database. I have the same problem on a Drupal site. The module I'm using stores latitude and longitude data in the database. If you look at the terms of service referenced on the page jmort253 pointed to in his answer, you'll find this:
(from https://developers.google.com/maps/terms#section_10_1_3)
10.1.3 Restrictions against Data Export or Copying.
(a) No Unauthorized Copying, Modification, Creation of Derivative
Works, or Display of the Content. You must not copy, translate,
modify, or create a derivative work (including creating or
contributing to a database) of, or publicly display any Content or any
part thereof except as explicitly permitted under these Terms. For
example, the following are prohibited: (i) creating server-side
modification of map tiles; (ii) stitching multiple static map images
together to display a map that is larger than permitted in the Maps
APIs Documentation; (iii) creating mailing lists or telemarketing
lists based on the Content; or (iv) exporting, writing, or saving the
Content to a third party's location-based platform or service.
(b) No Pre-Fetching, Caching, or Storage of Content. You must not
pre-fetch, cache, or store any Content, except that you may store: (i)
limited amounts of Content for the purpose of improving the
performance of your Maps API Implementation if you do so temporarily,
securely, and in a manner that does not permit use of the Content
outside of the Service; and (ii) any content identifier or key that
the Maps APIs Documentation specifically permits you to store. For
example, you must not use the Content to create an independent
database of "places" or other local listings information.
(c) No Mass Downloads or Bulk Feeds of Content. You must not use the
Service in a manner that gives you or any other person access to mass
downloads or bulk feeds of any Content, including but not limited to
numerical latitude or longitude coordinates, imagery, visible map
data, or places data (including business listings). For example, you
are not permitted to offer a batch geocoding service that uses Content
contained in the Maps API(s).
Parts b and c really make it sound like what you and I are trying to do is a no-no. Am I reading this wrong?