Another benefit of having stable identies / surrogate primary keys is that any relations (FKs) will be much simpler.

Sure, like the post poster you replied to is pointing out, you _can_ use natural keys, and then also relying on dates or other parts of the data - but creating a relation for that can end up being extremely cumbersome.

- Indexes generally become larger - relationships become harder to define and maintain - Harder for other developers to get up to speed on a project