No, I'm not talking about car engines - so let's forget about them for a moment. I mean shopping engines.

Shopping season is here once again. As you observe a good number of online retailers have maxed out paid search campaigns, raised ad media buys, and drive SEO folks bloody busy. But to boost incremental sales volume, these retailers should look no further than the major shopping engines.

At present, the three biggest players include: eBay's Shopping.com, Scripps' Shopzilla, and experian's PriceGrabber. How big has online shopping become? In the recent Hitwise study, it was found that 10% or more of all traffic on major search engines is sent to shopping property.

The burgeoning online shopping industry was backed by 2 compelling forces: the vertical creep and the vertical listings. The latter is shown at the top of organic search engine results and below top sponsored listings. They are also shown by shopping engines using aggressive SEO and SEM techniques.

What does this means? Marketers and shoppers should be clever in riding the hype. The advantages are numerous. But the drawbacks are just as overwhelming.