No I'm not an expert. As I see it if you publish something and the creation date is recorded it would be valid evidence later on if someone managed to patent or register the design somewhere else. Of course none of us are going to be able to afford to fight a legal battle so it's probably all academic anyway.
It does bother me when I see things popping up on Kickstarter that are using open-source technology and claiming it to be their own design, even more so when commercial companies manufacture Mendel Prusa's and the like and make a profit from open source designs.