It's often said that ads need to be entertaining because the entertainment allows us to 'smuggle in' a product benefit - the bit that is the commercially effective part of the ad.

I agree with the smuggling theory, but I actually think it works the other way round.

In other words, I reckon the function of the product benefit is to justify the entertainment. And it's actually the entertainment that is the commercially effective part of the ad.

Take this new ad in the Got Milk? campaign.

The product benefit is "if you drink some milk before bed, you sleep better." But this is just a pretext. The overwhelming volume in milk comes from kids drinking it, and adults putting it in their cereal and coffee. The reality is that very, very few people drink a glass of milk at bedtime and even if this ad were to double that number, its impact would have been negligible. No, the sleep enhancement may be a true product benefit, but it's not the business-enhancing part of the ad.

The ad will be effective because it's cool and funny. (Okay it's not the coolest or funniest ad ever, but my point still stands). So people will continue to feel good about buying it. The worst thing for any product is to become lame. Products that are seen as dated or naff don't sell. Period. This ad will do a good job of keeping milk seeming fresh, if you'll pardon the pun. So the effectiveness of the ad IS the entertainment.

Of course, that doesn't mean the product benefit is irrelevant. Far from it. As I said above, the product benefit is essential, because it allows the agency to smuggle in the entertainment. A comedy sketch (like this ad) has to be about something, and furthermore we find it satisfying when an ad is well-constructed around a product benefit, because it makes the sketch seem cleverer, and the comedy more justified.

I wonder if it would ever be acceptable to say to a client "the strategy we propose is that you do ads that are cool and funny." Probably not.