What I've seen in quite a few flats is that at the entrance floor there's a floor plan with names, so if you know to whom it is addressed and you have the right building you can deliver it. I've even seen more curious scenario's on islands in Greece for example where all you need to know is the person's name and the town they live in, the mailman does the rest since they make it their business to know who lives where :).

People can get very creative when it comes to these things. There's a very common concept of "old lady surveillance" in the Mediterranean where the elderly sort of function like a bottomless address book if you ever need to get directions and can usually complement a police report too, since they just tend to observe everything going on in their neighbourhood.

As far as mail distribution goes, I think since you can reverse the lookup to find the actual geographical location you could do that in a mail distribution centre and bundle things up for delivery, much like postcodes are used.

Or how does 911 know which fire company to notify when you call and say your house is on fire? When the right fire truck is en route, which street do they turn down to reach you?

Or when you ask the local pizza parlor, "Do you deliver to my address?", how long does it take anyone to figure out the answer to that question?

Or when you want to take a taxi from point A to point B, and the small local taxis charge flat fees between different neighborhoods -- as many do -- how do they give you a fee estimate without plotting both points on a map?

Addresses need to be more useful than GPS coordinates as well as more memorable, or else you've just turned every-day life into the sport of orienteering.

From the website of the company the article is about (http://what3words.com/) it seems they're targeting the use case of those without "adequate existing addressing".

So an as MVP accurately/deterministically identifying the location you live could be super valuable, going beyond that in the ways you described would be SUPER useful but maybe even this would be enough to add value!

Whether this is the right method of doing it is another question.