jbboon: I'm not sure the location it the thing.
Location certainly has to play a role.
The reason is that many of the ads I'm seeing are for local businesses. For example, one is an ad for a tire and auto center for auto repair. There's no way that ad would be shown in other parts of the country. And before Tuesday's primary, some of the ads were for those running for election in Michigan.
So, if someone lives in area where the advertising company doesn't have very many clients then users in that area would have access to viewer ads to view.