What are the pros and cons of using multi column primary keys?

I think it's almost always better (from an application developer standpoint, at least) to make the primary key an auto-generated key, and create a UNIQUE constraint and an index on the multiple columns.

• With a single auto-generated primary key, you'll be able to easily add references to this table from other tables.
• Auto-generated primary keys work more simply with ORM libraries.
• Also, if your uniqueness constraints change in the future, you don't have to change the existing primary keys.

I've run into several headache-inducing situations because a DBA thought that a multiple-column primary key would always be sufficient, and future requirements changes proved this incorrect.