How many of you use foreign key constraints and References in your database schema?

At the day gig, they use FK constraints and References in their Oracle database schema. Honestly, I got into that years ago with VFP but then kinda fell off that wagon over the years, preferring to just handle some things in the BizObj of the solution rather than put more rules in the backend database. The idea was that if I changed backend databases, I wouldn't need to rewrite a whole bunch of specific DBMS code.

Where's your preference in design with these in mind?