You could view the FamilySearch Family Tree as just another step in the evolution of online user defined database programs, but I would like to submit that the concept of a unified, source-based, lineage-linked, family tree presages a fundamental and positive revolution in the way genealogy is done. Further, the revolutionary nature of the program will be minimized by those promoting the program, for the simple reason that they do not want the users to become overly concerned about the program itself. They would also like a smooth transition from New.FamilySearch.org to the "new" program.
Let's look at the present method of doing genealogy. I have my information about my family and I "share" it with others, either by sharing files or putting my version of the family online in a family tree program. If someone spots a similar family member in another user's family tree, then the two people can "communicate" their common ancestor, usually by showing the other family tree as a "source." The programs themselves make "suggestions" of other user's trees that might have similar or the same ancestors. In some very limited cases, family collaborate in building a "family tree." Of course the limitation is that unless someone is aware of the "family" they cannot participate in the family tree.
The relationship and interaction between the user participants in online family tree programs and other file sharing arrangements, still leaves each of the participants with their own version of the tree. If I choose not to add any sources to my family tree, that is my business. If you decide to source every event, that is your business and I really don't have to even look at your sources or even look at your tree.
Now then, what is the revolutionary aspect of FamilySearch Family Tree? It is the idea that everyone looks at the same family tree. If I enter my data into FamilySearch Family Tree, it ceases to belong to me and becomes community data. Any changes or additions I make to the unified family tree belong to my entire family. Any one can change any person or event. Any one can add sources or not. But when I am looking at a particular ancestor, I am looking at the cumulative consensus of my entire family, not just my version of the family line. Because only one individual, no matter what name, date or place is inserted, can exist at every node in the family tree pedigree, there has to be a consensus.
New.FamilySearch.org tried to reach this goal, but had a fatal flaw; the files were not unified. If I added information, no one really had to deal with it. Why? Because my data just became one more combined record with up to hundreds of records for one individual ancestor. In addition, none of the information could be changed. It became difficult, if not impossible, to distinguish the correct information from the incorrect information.
But wait, FamilySearch Family Tree is not fully implemented. What does it need to become truly revolutionary? First and foremost, it need a way to eliminate duplicate entries. They are promising a "merge" function, but unless this truly gives the user a way to eliminate duplicates, the program will become just another online family tree program. If every one of my relatives is looking at exactly the same information I am looking at, that move collaboration out of the "voluntary" category into the mandatory category. Also, distant, unknown to me, relatives, that come into the program and look form their "relatives" will also see exactly the same information I see and that I enter into the program.
If you think about this for a while, you will realize that this will revolutionize the way genealogy is done. What if I were searching for an ancestor in the 1700s in New England? If I found some information and put it in my "online" family tree, another one of my family members may or may not ever see that information, especially if they have their own "family tree" online. But if I enter the information and the source in FamilySearch Family Tree, we will both be on the same page, looking at the same information.
This whole idea is entirely contingent on FamilySearch Family Tree living up to its promise. If the program has some flaw that allows duplicates, then the unified idea will not work. Right now, we are still waiting to see if it lives up to its promise.