Putting in my vote for a layer lock that ensures objects on locked layers aren't editable.
The lack of this capability means that we cannot structure our documents effectively. We use layers to isolate and select geometries that we want to edit via locks. Just now, I wasn't able to create a series of buttons and duplicate them without duplicating the underlying background layers, which makes layers-as-structure effectively moot. In the desktop app, and other similar apps like Photoshop and Illustrator, this is standard. You use layers to isolate related geometries for editing, but also to create a reasonable document structure.