• by Kaila Colbin , Featured Contributor, September 7, 2007

A couple of months ago, I participated in a 3-part series aimed at defining a search engine. In my contribution, What Is Not a Search Engine, I made the claim that a Web service that doesn't search beyond its own e-borders is not a true search engine.

This claim was pretty well rebutted by David Berkowitz' Search Insider piece on Tuesday, which makes me grateful that I now write for Search Insider as well, so we can have it out with each other center stage :-)

I posit that search can be divided into two categories: the passers and the catchers.

The passers are those whose primary business is to direct traffic. They're not aiming to create a sticky site. Google exemplifies this business model. Its primary job as a search engine is to get you somewhere else. If that somewhere else happens to be on the site of an advertiser who's paying Google, well, so much the better.

A passer's primary aim is to serve up the content the searcher is after, with organic and paid search results that are roughly equal in relevance. If the organic results are too good, nobody will click on the ads, and if the paid results are too good, it'll seem like a scam.

Either way, the aim is not to keep you; it's to keep you coming back. If the paid and organic results are equally relevant, volume of visits is what will drive paid click-throughs.

The system is set up so that the primary motivation of the passer is to deliver exactly what the user wants.

The catchers, on the other hand, are those whose aim is to keep you on the site as long as possible. MySpace, the fourth largest search engine from David's article, is a catcher. EBay is also a catcher.

In last week's Behavioral Insider, Steve Smith interviewed Scott Shipman, eBay's senior counsel, global privacy practice, and Kasey Chappelle, director of privacy for the marketplaces division, regarding the company's new AdChoice program. Shipman made this intriguing comment:

"Off-eBay ads are created by eBay with the idea of driving traffic to eBay. Advertising on eBay up until recently have been very sparse and through relationships with Google internationally and Yahoo domestically. We are about eight to ten months into programs where they host ads for us on our site. The key notion, as you can imagine, is that we don't want to cannibalize the activity on the site and direct people off of the Web site. So we are very sensitive to where they appear and the content they are advertising."

He repeated the metaphor a bit further down:

"From a cannibalization standpoint on eBay, naturally we want the ads to be as customized as possible on eBay because, one, we want to make sure that either it is as relevant or tailored as possible to the individual so we don't cannibalize the site itself."

Catchers have to make sure that the content on the site is good enough to keep people there, and trustworthy enough for people to have confidence in the quality of ads and search results.

The system is set up so that the primary motivation of the catcher is to deliver exactly what the user wants from the existing site content.

Please do not misunderstand me here. There is absolutely nothing negative about being a catcher. It is simply a different business model from that of a passer.

If I've already determined that a catcher's site is where I want to be, it stands to reason that I want search results and ads to guide me within the site. On the other hand, if I've got an open query, I want to make sure that I'm not constrained to results that serve the site before serving me.

Being a catcher is the reason why, even though Facebook's site search is proprietary, they're not a search engine. EBay isn't a search engine. Technorati isn't a search engine.

Perhaps these sites aren't interested in becoming search engines; if they are, they'll need to learn to pass the ball.