I have been a genealogist before the internet and started with ancestry.com when membership was very small. One reason their database is so vast is directly related to their policy in not allowing the database to be shared (LE, med. Insurance etc). Even inside ancestry, you can make your results private. I also uploaded my DNA into GED to be helpful. It only takes one and you get genetic info on two separate families (mother/father). But if you track those two parents…..the information expounds.
Those like me that have used reversed genealogy to reunite adoptees and birth families, identify John/Jane Does and now perpetrators in crime know how valuable these databases are. Still, if you came to ancestry, paid money for their specific test, understanding that it does not go beyond their walls 20 years ago or yesterday, could be problematic if they changed their policy. How ancestry keeps a secure wall is only allowing DNA result from tests purchased by them and sent by to them. Otherwise, any LE could just upload a sus DNA. Ancestry does not allow outside uploads.