The increasing number of people involved in your research soon outstrips the ability of of anyone to remember all these relationships and without a dedicated and concentrated effort, parts of the lines will soon be all tangled up. I have a standing challenge to anyone with a record of any substantial family history, that I can find inconsistencies and mistakes in your family lines in less than 15 minutes. I have been challenged again and again and I have always been able to find the problems.
If tangles are the rule, then what hope is there?
Part of the answer lies in systematically documenting every addition to your family tree. The rest of the answer will come through a cooperative effort on the part of huge families. This is basic concept behind the development of the FamilySearch.org Family Tree. It is a "unified" and self-correcting program. The unified part means that everyone can see and work with the information. The "self-correcting" part is a little more difficult to understand. As I say in classes and discussions over and over: Family Tree is the solution, not the problem.
Let me give an example of what I mean.
Let's say I am working on one of my family lines. I have a limited amount of time and limited access to the documentation about my family. However, I have a pool of relatives who are descended from the same ancestors. Since all of us have access to the same data pool in the Family Tree, we can all add, correct and document. Together, we have more time and more resources. Unfortunately, many people focus on the negative aspects of cooperation. They see any changes to the Family Tree as a threat and not as cooperative help. This is primarily a result of thinking that "I am right and everyone else is wrong." The reason the Family Tree is self-correcting is that the people with the most correct information will ultimately prevail in any interchange.
Time for a hypothetical situation. Let's further suppose that you have a "relative" that is mentally, not quite stable. He or she disregards logic and "messes up the content of the Family Tree" continually. Guess what? This was going on all along. The data in the Family Tree is derived from "all" of the previous submissions that were available. The mess is already there. So how do you sort out the additional stuff put into the Family Tree by your less than responsible relatives? The answer is that they were there all along. The difference is now you can see them and their work in real time.
If you view the changes and the magnitude of the work as "your personal responsibility" then you are going to feel overwhelmed and frustrated. The answer lies in the first point: this is a unified tree. You have to form coalitions of family members, perhaps with people you do not now know. You do this, in part, by talking to people. In my family, we are slowing creating these coalitions of responsible relatives. I now have a number of family members that can work on maintaining the integrity of the Family Tree on various lines. Accurate information and documentation is flowing into the Family Tree and will eventually overwhelm any minor problems caused by uncooperative and irresponsible people.
The Family Tree is like a vast battlefield. The soldiers in the battle are the researchers. The opposition forces are simply irresponsible and in some cases incompetent. It is not much of battle really. Adding sources and documentation, with extensive explanations where appropriate will prevail. The rallying cry is "Truth will Prevail."