I think they are a good idea. There was a news report here a little while ago demonstrating how it works.
Looking through some of the posts here, I don't think people understand them very well.
While some countries have safe havens, they aren't always anonymous. Obviously thats the same for adoption.
Young or vulnerable women who are in a terrifying situation, scared of the consequences or backlash, may want to be anonymous. They could be victims of domestic violence, very young with disapproving parents etc. They clearly feel like adoption or safe dropping isn't an option, otherwise people wouldn't live their babies in bins, toilets etc (except those with severe mental illness that arn't thinking right).
Also baby boxes don't just leave the kid in there for hours to fend for themselves. They are heated, and as soon as it is closed on the outside, it triggers an alarm. Whoever closes it has a few minutes I believe to make themselves scarce. Then someone linked to adoption services can pick the baby up and it can receive immediate care.
My only issue with it, I don't know how it works if someone gives up the baby that isn't the parents and the parents want their baby back. Using the disapproving parents of a teenage mother example, for instance, what would happen if they put the baby in the box and the teenage mother knows nothing? Could she get it back or what?