Aside from setting a read-only tag I don't - seems like a dangerous thing to be doing - why are you sharing?
Apologies for not clarifying in OP, I was significantly sleep deprived when I initially posted.
I'm on a shared corporate network and other members of my group have access to the files I work on because we all work on them in some capacity. I am the main architect, but I still have to be cognizant of whether the workbooks are being tweaked. My group members don't need my permission to access the files, and the files are utilized on an as needed basis so there's no structure in place of "member A completes work, hands off file to member B, etc."
How about some basic source control? If you search the forums for the "github" keyword, you'll see a few people discussing this. That way you could force better behavior.