The thing I most dislike about w3w is that there's no spatial locality or reference
By that I mean, given two addresses, there's no way to guess where they are or compare them and determine how far away they are.
Addresses obviously have this property. I can intuitively determine that "42 Wallaby Way, Sydney, Australia" is next to "44 Wallaby Way, Sydney, Australia", and the same holds for GPS co-ordindinates. Even postcodes - while not deterministic - often cluster together.
With w3w though, where is levels.nine.coins? How far is it from fork.scruples.wage? It's a total mess.