I've been working on a larger project (for me) lately where there will ultimately be 150+ tables. On most of the other projects I've done, I haven't given much thought to normalization. I've looked back on them and most of them seem to be normalized anyways. On this project I've started really looking at how tables are related, etc.

The one issue that has come up is how foreign keys are handled in the normalization process. I started noticing some of my tables (let's call it "Main") have a foreign key to another table ("middle")a foreign key to some third table. Is it bad form to include a direct foreign key in my "main" table? Or is this a case of "it depends"?