I can't say I spend any time on enforcing referential data integrity since I moved from Access to SQL years ago. I've never had a problem in 10 years. As I see it, enforcing data integrity is to compensate for something that should never happen in the first place. It would be like adding if/then/else statements in .NET that would never be executed unless somewhere else in your program you did something incorrect. What it comes done to, is that it is hard to justfy spending time on it on a per application basis.