My friend and I have bought sponges, they don't work. So when I place down the sponge I told my friend to test it out. He easily broke the piece of dirt next to the sponge. I also want to add my friend to my region, so we are protected by the sponge is that possible?
It is a current bug it will be fixed soon. If you get griefed and provide evidence including you placed down a sponge before/during the grief the griefer will be banned.