How much information from highly secured RDBMSs is leaked and lost on a daily basis? How much of that leakage is prevented by the database's security mechanism

How much information from highly secured RDBMSs is leaked and lost on a daily basis? How much of that leakage is prevented by the database's security mechanism, vs. that of the application connecting to it? And to pick on certain things - does SSL connections REALLY matter? If you're running over an untrusted network (bad idea, in general), why not just use IPSEC?