(I don't know the source, other than the ever-vague tumblr post, so if you know please tell me!)
I love interesting beds. Beds without frames (sometimes, but not always.) Beds in weird places. Beds I make out of putting two chairs together! But I really love this idea. I would gladly add in the walls and french doors to a bedroom just to have the feeling of actually being a baby bird in a nest. I don't know what it is about it... while I enjoy the concept of being so tucked into safe walls and corners, I'm not the kind of sleeper who absolutely needs to be beside a wall.
I'm not even going to try to explain why I love this, I just do.
Though the picture doesn't add much context for the use of this bed, I can imagine it would be superb in a house with few bedrooms or no excess space but a nice pre-existing nook to use as a guest bedroom.
The only downside is that I spend a lot of time doing things in my bed. Oh my god, stop it. I mean reading, and writing, and computering. I know this is deeply frowned upon by spiritual advisers and psychologists alike, but it's a habit I don't foresee breaking anytime soon. Where do I put my book when I'm done? Open the door? Sleep with it is not an option! If there was some way to safely incorporate a shelf...
Anyway, I could go on about beds forever. And I will. Soon.