Eastman's Online Genealogy Newsletter: Why Cloud Computing Makes Sense for Genealogy:
. . . . "Looking at genealogy applications, we see that cloud computing is in its infancy. There are only two true cloud computing genealogy applications today: FamilyTreeExplorer.com (formerly known as PedigreeSoft.com) and OneGreatFamily.com. FamilyTreeExplorer.com has not enjoyed much commercial success in the marketplace. Indeed, most genealogists have probably never heard of FamilyTreeExplorer.com. OneGreatFamily.com has been more successful and continues to attract new customers.
While both products qualify as 'cloud computing' services, the two are very different in operation. The most notable difference is in the decision of whether or not to share data. OneGreatFamily.com has only one database, and all customers share it. Everyone can see everyone else's data and can link their families together when they discover information about common ancestors and other relatives that other customers of the service may already have entered. FamilyTreeExplorer.com, however, provides a separate, isolated database for each customer. There is no linking to pre-existing data in FamilyTreeExplorer.com. FamilyTreeExplorer.com does allow the customer to grant access to others, if he or she wishes to do so. Nobody can ever see the customer's data, however, until he or she grants such access to others on an individual-by-individual basis.
No discussion of genealogy cloud computing is complete without a mention of WeRelate.org, New FamilySearch.org, The Next Generation, or PhpGedView. These products vary widely in design and implementation, but all of them allow multiple people to run genealogy applications in distant computers. In addition, the latest versions of RootsMagic and AncestralQuest have the capability to exchange data with cloud computing databases.
However, neither of these last two products uses cloud computing for its core functionality."
and I would add any fanily tree you can edit and add to online