What.cd had a very simple data model and it had the same issue as many music sites trying to fit it into a simple schema (and not a more sophisticated one like MB). The first issue that comes to mind was artist with the same name, these ended up being the same artist (Just like on Last.fm) if not split by hand by changing the artist name.

The schema is here in case you are curious: https://github.com/WhatCD/Gazelle/blob/master/gazelle.sql

I really miss what.cd

How do you feel about redacted? It seems to operate in the same spirit (if not backend code)

Got nothing against them, but it's still not what just like what wasn't oink. Every time there is something lost you just can't get back.