Is there any security risk in having many foreign keys referencing a single table? I have a teacher who told me that having a database with a table that's referenced by around 60% of the other tables was a security no-no. The problem is that he failed to explain why it was a security risk.
This stretches the bounds of credibility.  The only thing I can think of is that by deliberately causing referential integrity errors the attacker is able to harvest the error messages and derive information the underlying schema.

However, if the attacker is able to do that you have bigger worries.