Required? To me, updates on projects, discussions on materials needed, and then a run down on details that'd be needed to talk to any outside customers or vendors so you don't have to.
Everyone else? Well, that wouldn't be required unless you did a collaboration. Then it'd be nice if you talked with the person you're collaborating with if just to make sure you're on the same page. Otherwise? People might try and talk to you, but it wouldn't be required.