Thoughtless act: Doorknobs as hooks

I noticed that in my apartment, I'd been using the doorknobs of the closets near the entryway to hang my tennis racket and umbrella. It was just a convenient place to put these items that I usually grab as I go out the door, without having to leave them on the floor. I also often hang my purse on the door of a bathroom if there is no hook. This weekend I went to the beach with a large group of people, and in the house there were far fewer bathroom towel racks than people. I noticed that tons of closet and room doorknobs had towels and swimsuits hanging on them to dry. The problem with this was that I couldn't open the door without touching somebody's wet swim trunks (yuck.). A possible design solution could be to have hooks that can be folded into the door (camouflaging well) when not needed, but can be folded out to accommodate extra hanging space.