As explained by the website:
Community Trees are genealogies from specific periods and localities that have been linked according to family lineages. Many trees include associated documents and images. Each community tree is a searchable database that allows views of individuals, families, ancestors, and descendants and gives various options for printing.
The scope of projects may involve members of a small villages or townships who work together to form a family tree of all known residents of the community for a given time period. Some are projects involve (sic) genealogical and historical societies that work with FamilySearch to index several sources of data to link them to common, lineage-linked genealogies of a targeted geographic area.The database that I refer to in the introductory paragraph is the Royal and Noble Houses of Europe. This database is described as follows:
This database contains individuals ranging from A.D. 100 to the 1800s; includes ancestors and descendants of Clodion "der Langhaarige" ancestor of the Merovingian kings; Gorm "den Gamle" of Denmark; Charlemagne of the Franks; Wladimir I Swjatoslavitsch "der Heilige" Grossfürst von Kiev; Louis IX of France; Edward I of England; Charles I of England; and Spanish Kings of Navarre, Castile and Léon with many other European royal, noble, and gentry lineages with Colonial American connections. UPDATED Jun 2013By the way, there are 323,307 individuals in the Royal and Noble Houses of Europe database.
The Community Trees project has databases from Australia, the British Isles, Canada, England, Europe, French Polynesia, Iceland, India, Ireland, Italy, Latin America, Liechtenstein, Mexico and many, many more.
Why does a resource such as this go so unused? My guess is that there is simply a lack of visibility. There are hundreds or even thousands of such websites on the Internet and the noise level when you are searching is so high, it is unlikely that you will ever find these low-key, but highly useful types of sites.