I have taken the liberty of copying and showing here what one of my distant relatives has on her home page -
"A warning to anyone who wishes to exchange information with me. If you send me information, it will be shared with other genealogists, through this webpage and only living person's birth details will be hidden. If you do not feel comfortable with this attitude or want to hide family secrets, do not share them with me! I don't want to know, frankly. Keep your secrets to yourself, please'
"Genealogy is for sharing, without sharing it has no purpose! Preserving the past is best done by sharing the past, not leaving it in the hands of a few!"
I have always liked and fully agree with my relatives views. However, everyone has their own views and thoughts on this subject. We can make our own decision when setting privacy for our sites and also, only make family we can trust, as full members.
However, I do get what you are saying about taking what you write and having it copied, if they aren’t giving you credit as their source. Anything you do not want to share should be able to set private.