[portsnadaptors]

I don't think building an abstraction over the data layer is just to make it easier to change your database. The abstraction can define the data access patterns upfront and minimize bespoke data access code. I've spent a lot of hours trying to untangle ORMs and other data access code from business logic. I've found that extending an abstraction to support a new access pattern (that you really need) is much easier.

[rlabrecque]

This is one of the bigger discussions I've been involved with lately; and I agree it really comes down to "bespokeness".

When you have a 'system' which is 500 LOC, and 10 usages of that system totaling 10 lines each; compared to 10 bespoke implementations of 50-100 LOC each... you get into a spot where the system is battlehardened because of all the users, while the bespoke implementation have issues all over. Then when someone goes to add the 11th use-case of this; they are going to learn from and copy/paste the other version, probably exposing some latent bug in the bespoke version.