Once the data is put in, the garden becomes part of the user's "profile" on the site. Others can examine it and make suggestions about what to plant, how to amend the soil, etc. User can log the things they do and upload photos (or use automated sensors and webcam to send periodic updates). You can "star" someone's garden to keep track of it and see how well their decisions worked.
Would be a great tool for experienced gardeners with too much time on their hands, and busy newbies (who are nerds like me) to get free access to distributed knowledge to learn how to grow food in the back yard.