This question is a verbatim quote from
The answer given there is:
A. This is not advised because FRS does not provide distributed file locking. Depending on the update patterns of users, the lack of distributed locking might cause one user's update to override another user's update. If the collaboration is such that end users are not writing to the same files simultaneously, this most likely would not be an issue.
What's wrong with this picture? At some instant, be it a "collaboration scenario" or not, I might have 2 or more users looking at and even trying to change the same file. Usually, one gets the "This file is in use by another user... Open read-only copy?" dialog. Is this piece of drama telling me that while I use DFS and FRS this "Open read-only?" dialog might not appear? Or might not function correctly? Heck, at any instant of everyday use there is probabalistically a few users wrangling over rights to the same file! Reduced to the absurd, this statement implies that DFS and FRS are good only for single-user systems?
Tell me it ain't so! 400 points for potential brain damage while thinking about this.