In researching this piece further, initially by bouncing ideas off fellow columnists and then by reading research commentary by JupiterResearch's Niki Scevak and Hitwise's Bill Tancer, I've softened up... a little.
My biggest problem remains with the definition of vertical search. What is a vertical search site? Below is a definition that is entirely my own, vetted by no one, but it's a starting point.
A vertical search site or application must exhibit four key characteristics:
1) It focuses on a specific category.
2) The primary functionality revolves around search.
3) There are multiple competing content providers contributing to the results.
4) The natural results are ranked by relevance.
To better understand the definition, let's look at examples to see if it might affect how we perceive vertical search.
Google: This is easy. Its broad focus disqualifies it from being a vertical search site. Froogle, its shopping site, qualifies as vertical search. Google News is trickier. One can peruse Google News much in the same way one reads a newspaper: Scan the headlines and read what's interesting. Searching aids the functionality, but do users see the site has a headline aggregator or a news search source?
Yahoo!: Clicking any of the tabs from the home page such as "News" and "Products" points to a clear search focus. However, News.Yahoo.com is heavily focused on browsing, not searching.
Now we get into an even murkier distinction. Does it matter if someone's searching or browsing? Searching is more active and the user has more control. Yet in both, the site must make assumptions to return relevant results and organize them in a logical order. Searching and browsing are different enough that the distinction merits the fourth rule above.
Monster.com: Vertical search site? The first two definitions apply perfectly, especially once you click "Search Jobs" on the home page. There are also multiple competing content providers, in a sense. AOL and MSN can vie head to head to attract the same interactive ad sales professional or programmer. Yet something feels wrong with adding Monster to the list. Let's compare Monster to a 'truer' job search site.
Indeed.com: Here, multiple job sites are included, and the interface is entirely about search. Contextual ads from Google foot the bill. Any job site can take part, and Indeed directs all visitors to the participating site. This is especially appealing for users, with little upside for Indeed.
SideStep: This travel deal-finder partners with airlines (several of which are through its alliance with Orbitz), hotels, and car rental companies to scour sites for the best deals. Its browser toolbar has logged over 7 million downloads, and users can now search the site directly. SideStep is the reason why I included "site or application" in the definition; other applications for mobile phones and instant messaging could also fall under vertical search.
Ticketmaster.com: It meets every requirement. Anyone can request to sell tickets through the site, and while the search functionality is subtle, arguably few people go there saying, "I have $200 to blow. I wonder what's in town?"
Citysearch: In a similar vein, it's a local and vertical search site that begs yet another question: Where does local search end and vertical begin? Are they mutually exclusive or overlapping?
eBay: Count this as a vertical search site and you need to up those industry forecasts. How different is eBay from Yahoo! Shopping? With the hybrid paid inclusion (eBay - to list items; Yahoo! - to enroll in merchant services) and pay-for-performance models, their DNA has much in common. I've wondered for some time about whether eBay would or should launch a search engine, and Amazon's A9 adds more credibility to the musing. Go to eBay and you're greeted with, "1. Find: What are you looking for?" In many ways, it's a search engine already. A vertical one at that.
CNET Download.com: Search for software downloads from an array of publishers.
Epicurious: Find recipes culled from various sources.
Internet Movie Database (IMDB.com): Search for information and news about every actor, film, and TV show. The Unix version of the site dates back to 1990, making it one of the oldest online search applications that ever existed.
Are we heralding vertical search too late? Are we defining it too narrowly? Can a site be vertical and local, designed for searching and browsing? Are we too hung up on names?
If you want to be humbled, ask the users, the customers.
I was instant messaging with a friend as I finished the column, and she asked what I was doing. I tried explaining vertical search to her, and even after spending hours writing about the definition, it proved remarkably difficult - and this is to a PhD candidate. She asked, "What are you possibly writing about [vertical search] to make that interesting?" I said, "It's the hottest topic to talk about in the search business." She asked, "Why?"
Let's honor the customers' wishes, stop talking to ourselves, and get back to work.