“Of course,” it’s more complicated than advertising does or doesn’t work, but there’s a real question. Some advertising works some of the time, depending on your goals, but there’s a real question how well advertising works in a world of many evolving channels and increasingly fragmented mindshare. In this world, “of course” we’re not sure that advertising works, and many advertising and marketing people are scratching their heads, trying to understand how to get attention for messages and make them “stick.” A brute force campaign via Twitter, such as this one, is arguably no better than spam, and unlikely to be particularly effective. (Email spammers were apparently successful given high volume and low cost, but antispam measures may dry out that particular well.)
Google “advertising doesn’t work” – interesting range of opinion.