This can also cause delivery failures the other way around - a friend in Germany once sent me a package but didn't bother writing the apartment number on it because she assumed the postman would use my name to find the right box. Instead it got sent right back to Germany. (Austrian bureaucracy is just as unforgiving as German, they just have different rules to follow...)
3 days later our postie knocked on our door and asked if this parcel was for us!
We don't live in a big city but still it is a town of 20,000 so not that rural where everyone knows you, so I was impressed that they cared enough to try to figure out the address. Granted the post code narrows the search down.
I am certain had it been shipped the other way the post office in Norway would have rejected it immediately for not being 100% by-the-book.
The postal office in Norway tries hard to deliver to the correct destination. I've heard of similar stories where they only had a name and a city to go on, and it was delivered at the correct location. During Christmas, they even have a team of dedicated "detectives" who tries their hardest to figure out who the packages should be sent to.
Once, someone I knew in Norway (ok, my sister again...) somehow managed to combine her old and new address when ordering something online. And that parcel back and forth between 2 cities for a long time... :)
It's even better than that. Unless you are incredibly rural or the street is tiny, most streets have at least two postcodes - one for the odd side and one for the even side. In most cases, there's only about 15-30 houses in a postcode, any more on a road and it's split up into smaller chunks.