When I was younger, my mother owned a floral shop, and she had this amazing door that she would use to spray paint against. I have used this door as my headboard for years-- but even in San Francisco, I just screwed it into the wall! No anchors, no studs, just straight, powdery, flaky drywall. I can't believe I lived in San Francisco for four years with this wedge of wood just hanging precariously over my head... not to mention the unaware who would bonk their head on the doorknob.
Once again relocated to an earthquake zone (and to make it pretty, of course), I added legs and thick bolts (with washers) to stabilize the door behind the bed. It now looks a proper headboard: whaddya think?