Two headlines, five days apart: "Search is no longer an after thought for brands" and "Why search doesn't really matter". Confused? Both headlines came from digital marketing site ClickZ, and illustrate the two sides of the search ad coin.

Search is a driver of intent-driven traffic -- "two thirds of people ... were driven to perform a search [after being exposed to an advertising message]. Then 39 percent of those people made a purchase," ">said Robert Murray, president of search-marketing firm iProspect. Sure, he's a little biased, but I'm much more likely to drop a product or brand name into Google to find more information than to go to a manufacturer's website directly. To ensure that sort of traffic ends up in the right place requires some marketing dollars be spent on search -- but only when tied to offline marketing and branding.

And that's where search -- and Internet advertising in general -- falls down.

To move customers down the "purchase funnel" from "I want X product" to "I bought X product" to "You should buy X product too" requires a wide variety of ad purchases on a wide variety of platforms. TV, radio, billboards and the like are great at driving brand awareness, but not as good at driving actual purchases and customer retention.

Search advertising is very effective at driving actual purchases, but there simply isn't enough inventory to drive every sale an advertiser needs. On top of that, without the TV and billboard advertisements, customers wouldn't be doing the searches needed to drive the sales. Search is an important advertising method, but it doesn't drive enough sales directly to be the one ad type used. As the ClickZ article points out, "if one were to ask the largest advertisers in the world to shift $1 billion of their budget into search, they simply couldn't. There isn't enough inventory to buy."

So, what is the answer? A balanced mix of ad spend, spread across a number of ad platforms, but not forgetting that search ads can be the final nail to seal a purchase -- which is good news for Google. Since search ads are so effective at actually driving sales, search ads should -- if advertisers are smart -- continue to drive significant revenue for Google. That's important, because Google makes 97 percent of its revenue from advertising -- and a huge chunk of that from search ads.

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