Co-Branded Ads?

I'm a little surprised that we aren't seeing more cross promotions as brands try to cut marketing costs without sacrificing their marketing plans.

Here's a starter idea for you creative types:
Combine car and grocery chain ads. Instead of demonstrating cargo space by filling the trunk of a car with generic brown bags, show the vehicle parked in front of an actual grocery store. Feature a smiling and helpful store employee helping to load the bags, and... bam! Two positive brand impressions for the price of one!

Just watch... Soon you'll see kids wearing the latest Wal-Mart fashions while playing at a McDonald's. Or formerly-flustered housewives having time to relax with a cool and refreshing Diet Sprite because they've changed laundry detergents to new Double Ultra Cheer.

If companies are going to insist on running old-fashioned P&G-style-formulaic-product-demo ads, they might as well save a little money in the process by sharing costs, right?