Does Viral Marketing Work?

Intuitively, viral marketing makes sense. It's free exposure. People like it. They tell their friends. It gets covered in USA Today. With thousands of people aware of your business, how can it not turn into clients?

How indeed.

The problem with this thinking is the same problem with traditional marketing. It's the belief that awareness is somehow valuable in and of itself.

But it's not.

My question is, how do you know it's not doing more harm than good.

Take Burger King's Subservient Chicken. It got a lot of attention, but did it increase sales? According to an AdWeek case study it might have, but the results are so vague that you can't rule out the possiblity that it had the opposite effect.

Or look at Career Builder's Monk-E-Mail. It's great! I love making monkeys talk. And my toddler, Eli, went into a fit of awe and laughter (and for that, I thank them). I even sent it to my friends. Now they're "aware" of Career Builder too.

But in either of these cases, where exactly is the point of influence? How do they amplify other components of a larger strategy? Or, are they just unstrategic, unmeasurable "awareness" campaigns that may or may not help the company?