It's the number one question of our client who are considering a PPC program with Google Adwords, "If I'm already ranking well in the organic listings, why should I pay for ads on Google?"

I usually offer up a few reasons including:

1. Like any marketing, you want to make as many impressions as possible. Therefore, having two listings on the page (one organic and the other paid) increases the number of impressions you make. It's often the second or third impression that actually results in a click.
2. Some users prefer to look at paid listings rather than organic listings. I know that's not true of everyone, but certainly some. Personally, I lean toward clicking on paid ads since I know those links are often more relavant to my search.
3. PPC ads allow you to carefully control your message and send users to a specific landing page, which often results in a higher conversion rate.
4. You need to protect your brand. Many web service providers (like Comcast) serve up paid results when a visitor types in a search phrase in their browser's address bar. Therefore, the only way to be seen by these users is to pay for placement. (By the way, we think this practice by service providers is a frustrating money grab and should be illegal.)

We've had two occasions at Interactive Strategies when clients went cold turkey and turned off their Google Adwords and other PPC programs. The results were surprising -- not only did our clients' paid traffic drop, but so did their organic traffic.

Finally, this article in today's New York Times offers some interesting proof of this interesting phenomenon and supports our theory that a PPC program can actually boost the impact of SEO.

http://boss.blogs.nytimes.com/2011/11/09/my-grand-experiment-turning-off-adwords-2/

While the author speculates that Google may boost organic rankings based on paid listings, we're rather confident the reason is based in a fundamental marketing principal: the more impressions you make, the more likely someone is to respond to your ad. So consider the PPC ad the first impression and the organic ranking the second impression.

If our theory holds true, it means that every dollar spent on a PPC program is even more valuable then we originally thought.