I am reading about NATURAL shorthand form for SQL joins and I see some traps:
These "traps", which seem to argue against natural joins, cut both ways. Suppose you add a new column to table A, fully expecting it to be used in joining with table B. If you know that every join of A and B is a natural join, then you're done. If every join explicitly uses USING, then you have to track them all down and change them. Miss one and there's a bug.
Use NATURAL joins when the semantics of the tables suggests that this is the right thing to do. Use explicit join criteria when you want to make sure the join is done in a specific way, regardless of how the table definitions might evolve.