I wrote:

by data integrity I mean that any DML that needs to be run in a transaction (i.e. where more than one operation needs to be performed) are wrapped in a single stored procedure

I should add that stored procs are also used to do access control. Access to the underlying tables is revoked from all but "privileged" users, forcing all access to be done through the stored procs. This allows the DBA/SQL developer to perform query optimization without affecting the client code, and it means that operations that need to be done in a single transaction will be done that way, because there is no way for normal users to access the tables directly.

Michael