Murphy beds have come a long way from the much-maligned folding beds of yesteryear. For one thing, they no longer spring up into the wall unexpectedly. Today’s Murphy beds might convert into a table or bookcase, or roll out from behind the wall leaving room for shelves or artwork. This article on homedit gives some stunning examples.
My neighbors have one that folds into a desk in their office/guest room. At Colin’s house, Abby has ordered two to be installed in the family room for overflow sleepers. My favorite concept might be this one, which takes up the same space as a desk, table, and open living room, and responds to hand gestures with no physical intervention required.
You don’t use your bed for most of the day, so it doesn’t really need to be out in the open. For guest beds, the use is even less frequent. (If you have a guest room, you probably already use it for some kind of storage, so a mattress consuming half the floor isn’t the best use of space.) A bed that folds or rolls away instantly gives you an extra 30-40 square feet when not in use. You can even build your own, and not for very much money. I love Murphy beds.