'Lag Sites' as a disaster recovery option, you may have already come across Introduction to Windows Server 2008 R2. After some digging, you'll find:
Recovery of deleted objects. Domains in Active Directory now have a Recycle Bin feature that allows you to recover deleted objects. If an Active Directory object is inadvertently deleted, you can restore the object from the Recycle Bin. This feature requires the updated R2 forest functional level.
So while this won't be a replacement for solid backups, it certainly should augment them well and allow admins to get data back quickly without the need for complex lag site arrangements, or worries that the deletion has occured before the backups have had a chance to capture it. As always, this is pre-release documentation and there are no guarantees made about the component availablity or even if it will be included yet. [Ned]