Just as the Justice Department is turning up the antitrust heat on Google, the competition in Web search seems to have gotten hotter than ever.

I’m referring to the long-anticipated debut of Bing, the supposed category-killer search engine from Microsoft. I read recently that Microsoft had already picked up two percentage points of market share in search queries since Bing debuted. This has enormous investment implications, since I’ve long recommended Google shares based on my belief that Internet search represents a rare natural monopoly. If this isn’t the case; if there are no real barriers to entry; if a Microsoft can penetrate Google’s defenses and upend its natural advantages, then it’s time to rethink Google and its prospects.

So what’s Bing? Let’s type the word into Google: “Bing is a search engine that finds and organizes the answers you need so you can make faster, more informed decisions,” says the first entry to appear, from Bing itself. “Microsoft is set to launch an $80 million to $100 million campaign for Bing, the search engine hopes will help it grab a bigger slice of the online ad market,” reports Advertising Age, item number two. And “Microsoft Bing: Much better than expected,” reports CNET, item No. 3. You can’t fault Google for disfavoring a direct competitor. Indeed, the headlines pretty much explain my anxieties about Google.

Now here’s “Bing” on Bing: The first item is the same as on Google, from the Bing Web site. Item two is “Welcome to the official Facebook Page of Bing,” and three is “Bing: a better way to search from Microsoft.” They are all self-promotional. The following item referred to Bing Crosby. There’s also a separate entry for “News about Bing.” Of the top three entries, two are about Detroit Mayor Dave Bing and one is about the meaning of “Bing” in Chinese. (One caveat: All search results may have changed by the time you read this.)

This was a generalized search request, which may not be Bing’s strong suit. I read (on one of the  Google entries) that Bing is really only trying to compete in the most lucrative categories, such as shopping. So let’s enter “Farmstead Ticking,” a Ralph Lauren china pattern for which I’m seeking a replacement. Google sends me first to eBay, which has just what I’m looking for in several entries. Next is shopping.msn.com, a Microsoft product, where another click connects me to Replacements.com, which has the item in stock. (EBay also led me to Replacements.com, but offered several much cheaper alternatives.)

On Bing, the top results from the same search unhelpfully included “Clock Ticking on Farm Bill Negotiations.” So I tried limiting the search to Bing’s “shopping” tab. What I got: 15 entries, all from Replacements.com. There may have been more, but I stopped after scrolling through 15.

This no longer seems much of a contest, but let’s try news, which I consider one of Google’s vulnerable spots. The problem is that the most recent items don’t appear first. My guess is that the Google search algorithm uses the number of clicks as an indicator of relevance, but the older a news item, the more clicks it’s likely to have generated. The most recent news, and thus the most relevant search result, is disadvantaged by its very newness. So let’s try “Ford earnings.”

The problem persists on Google: The top two news stories about Ford earnings are both from past fiscal years. The April 24 earnings, the most recent, ranks third.

Can Bing capitalize on this weakness with more relevant results? On Bing the most recent earnings report didn’t pop up in the top five results. I tried Bing’s “news” function, figuring it might lean more toward recent events, but instead I got several reports on Navistar earnings, an item on the Dallas Cowboys, and several items about actor Harrison Ford. Inexplicably, nothing comes up about Ford Motor Company itself.

True, the Bing home page looks nice, displaying a variety of attractive photos, including an inviting beach resort. But that’s hardly enough. Good luck to JWT, the agency Microsoft has reportedly hired to spend the $80 million to $100 million to get us to switch.

Every time Google has been presented with another supposed threat to its search prowess, I’ve done similar experiments, with similar results. I’ve held on to my Google shares, buying more on weakness induced by investor fears of competition. This may be another of those occasions. But don’t take my word for it. Try your own searches.

The New York Times Syndicate