You can actually prevent your members from editing your tree by going into Settings > Privacy and into the 'Members' tab. There you will the option to prevent members from editing the tree, and also from posting content to your site, if you wish.
I would like to stress that most of our users enjoy having their sites open for editing by their members, as a collaborative family platform.
Thank you very much to respond to my topic. Special thanks to the good news about editing the Tree. Feel little embarrass that I could thought that myHeritage had not given a few possibilities.
I apologise for the trouble.