I do not see any advantage in a lagged copy of a database. If any kind of corruption happens on a database we still have daily backup of the active DB which we can “activate” very shortly.
With lagged copy of a database, you still need a passive copy for high availability, you will end up with two copies of each database + the backup the active one . For me it is a waste of storage for what it brings.
This is a point of view worth considering. Certainly for some organizations lagged database copies won't add much value. Either the scenarios they are designed to protect against are not considered to be a high impact event, or the risks are mitigated in other ways (such as traditional backups).
For other organizations the logistics of restoring data from traditional backups make lagged copies more attractive, as the data is already available and within the control of the Exchange administrators without needing to engage with other teams or third parties.
And for organizations where traditional backups aren't used (which includes the Exchange Online service within Office 365) lagged database copies form a part of the Native Data Protection capability of Exchange Server 2013, which eliminates traditional backups.
What do you think, are lagged database copies a waste? Or do you see them as a valuable feature that you already use (or want to use) in your environment?