Ed has started to roll around a lot in his crib, so he's not always sleeping on his back. This is him napping today. This particular nap ended when he wound up on his stomach pressed up against the side of the crib and couldn't manage to roll himself back. We added the white "breathable bumper" after he woke himself up that way several times over the weekend. I guess it would be a rude awakening to roll over and suddenly have your face pressed against a wood rail. Without the bumper he also was getting his arms and legs "caught" in the slats. They weren't really stuck, but he couldn't figure that out on his own.
We never had bumper pads because of the cautions of the risk for SIDS. This is a very thin layer that is easy to breathe through. When I looked online to see if I could find a product like this, I found many parent comments like: "I bought this after I heard by baby cry in the night and found her with her head pressed into the corner of the bumper pad." Glad we never bothered with what is essentially a decorative item. We didn't spend a moment of the pregnancy considering "nursery decor" so it just never came up. After Ed arrived, we ordered a crib, mattress, and sheets and that seemed enough.