Does Internet Advertising Work?

An interesting quote from the show:

TADELIS: And we took a third of these D.M.A.’s, and we turned off all paid-search advertising. This was an extremely blunt experiment where we’re saying, “What would happen if we didn’t advertise at all?” And to our surprise the impact on average was pretty much zero.

It's interesting that many people are worried about deeply targeted ads, but here is an ad professional saying that this add had no effect.