I was surprised recently to find the my Great-grandfather, John Hamilton Morgan, was marked "Read Only" in the FamilySearch.org Family Tree. Here is a screenshot of the page:
This will likely occur more and more frequently in the Family Tree and it is important to understand why and how it happens.
The current basic reference is found in the Help Center for FamilySearch.org. The article is entitled, "One of my relatives has a restricted record." Here is a screenshot of part of the article:
You should be aware that these entries can and do change frequently. It is always a good idea to check with the Help Center entries before becoming frustrated over any change on the FamilySearch.org Family Tree.
What is happening here and only partially explained by the article, is that the Family Tree is a moderated wiki. This means that changes to the tree are not a Wild West shoot out, but the individuals in the Family Tree are subject to being "locked" and there are and will be more such locked individuals in the future. As the article explains, any changes to a "Read Only" individual must be submitted by the users and approved by FamilySearch.
In my case, the reason is likely because this particular ancestor was prominent in Utah history. Historical figures and other frequently changed individuals may also fall into this category. You need to be aware of this trend and realize that much of what we see today in the Family Tree is subject to revision.