The comment about using query plans to determine the columns used in joins is definitely a worthwhile approach.

This article was great and I wish developers especially would think more about foreign keys.

This may have been hinted at in the article but use caution when 'refactoring' an existing database that is used for a front end application. This may be obvious to some but often times the data integrity responsibility (incorrectly) gets placed in the application itself. So keep that in mind and don't rush out to reinvent the wheel. Although, definitely try to reinvent it where necessary.