> "*Really* big sites don't ever have referential integrity. Or if the few
> spots they do (like with financial transactions) it's implemented on the
> application level (via, say, optimistic locking), never the database level."
Some large sites don't even use data types!
http://www.thestar.com/News/article/189175
"in some cases the field for the social insurance number was instead
filled in with a birth date."
(search the archives for "OT: Canadian Tax Database")
Cheers,
Stuart.