Databases crunch numbers and do set based math like theres no tomorrow - no OOP language can perform as fast doing loops.

Hell yes! Single source for integrity and rule enforcement is where its at.

I've looked at LINQ and at first glance my instincts are saying looks good but why do this?

The only thing I can think is marketing gimick, and peer pressure - SQL has to be seemless with other datatypes. "Dumbass developers should only be using one access method period!"

Danger is poorly developed database structure and relationships will cripple it.