Well, if you built a huge build that took a few months, and some starfish 9 year old comes and steals it and says he took credit, you would probably change your mind about this.
1. Make a gallery topic about it.
2. Add hidden messages in it, that only you know of.
3. Even if he "steals" it, everybody would know cause he wouldn't be able to reproduce it.
Also, why is everyone obsessed with "protecting" their builds? If you build something cool, why not share it so that everybody can have fun with it?