Rumors are flying that Yahoo! (Nasdaq: YHOO) may decide today whether to accept Microsoft's (Nasdaq: MSFT) $44 billion merger offer. For Microsoft investors' sake, let's hope Yahoo! rejects the bid, or someone else rides to the forefront. This is an expensive offer for a second-tier product, whatever Microsoft CEO Steve Ballmer may contend.

The $1 billion in "synergies" he's hoping for in a tie-up would have to shore up a falling market share. As I noted earlier this week, the analytics firm Compete.com put Yahoo!'s market share at a dwindling 17% domestically, and the company considerably lags Baidu.com (Nasdaq: BIDU) and Google (Nasdaq: GOOG) in the large and growing Chinese market.

Based on December traffic, even in the aftermath of a Microsoft-Yahoo! merger, Google would command a kingly majority of the search market. The combined company would vault past News Corp.'s (NYSE: NWS) MySpace in terms of engagement, traffic, and page-view metrics, and it would surpass Google in unique visitors. But at what cost?

The market researchers at Compete examined both companies' statistics, taking into account three Microsoft properties: Microsoft.com, MSN.com, and Live.com. For purposes of comparison, they did not consider Yahoo!'s off-site properties, like Flickr or del.icio.us. They found that the two companies share 96 million visitors; the merger would thus give Microsoft a 31% increase in unique visitors, and nearly double its page views.

That means Microsoft's merger offer amounts to a whopping $1,186 for each of those new visitors. Now, one could argue that we ought to account for Yahoo!'s sizeable investment in Alibaba.com, and its presence in Europe, Latin America, Asia, and elsewhere. But while synergies may develop in attracting online advertising dollars, integrating a company the size of Yahoo! won't be easy for Microsoft. Buying Yahoo! also offers little else for investors; despite the company's strong brand recognition, you can get most of what it offers elsewhere -- and sometimes even more.

IAC's (Nasdaq: IACI) Ask.com has a great domain name for the search market, and it's redesigned the site to increase its usefulness and attractiveness. Still, its name recognition remains low. Given IAC's proposed split, unlocking value from Ask.com's online business would seem far easier task than trying to swallow Yahoo! whole.

Microsoft is a recommendation of Motley Fool Inside Value. Baidu.com is a Rule Breakers selection. Yahoo! is a former Stock Advisor pick. Any and all of the Motley Fool's investment services come with a 30-day free trial subscription.

Fool contributor Rich Duprey holds no financial position in any of the stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.