Enforced globally unique column names - natural joins on everything.
Throw an exception if a query requires a table scan (bonus points if it printed the statement that would create the appropriate index).
Translate all update and delete statements into inserts (enforced immutable data + versioning).
EDIT: I guess that doesn't really address your point of needing to join on a composite natural key though.
It ignores things like integrating with other systems. If I export my data to an OLAP database, I can't just cascade that key change through it without manual effort.
It also ignores managing historical data. Maybe I don't want that natural key update cascaded everywhere. In their example of hotel room number, if that public-facing number changed (which does happen), I wouldn't necessarily want that cascaded everywhere. For example, I might need past reservations/invoices from before the change to keep the old room number, to match all correspondence with the guest, etc. Okay, so maybe you don't automatically cascade everywhere, but then you need some way to link that old room number and the new room number in all of your reporting.
Bleh. That's a lot of headache that can be greatly minimized with a surrogate key, for very little drawback in my experience. Sure, I can imagine scenarios where the performance impact or additional storage could actually be a real negative, but for your average CRUD app, I think surrogate keys add way, way more value than cost.
