How many people do you know that even know they can do this, let alone know how to do it. Let alone would go through the process of it. Let alone would understand the ramifications for other site interactions.

non event. You and 17 other people might do this.

Presumably the aggregation sites would have instructions in big red letters at the top of every page.

If they're going to implement such a crazy thing, they might as well also block requests that have no referer.

Which inevitably leads to a kazaa/napster like escalation of arms where just about everyone disables referer headers, after which content providers lobby to make that illegal.