A viable challenge to Google?

The two companies have complementary strengths that ought to make them a tougher competitor as a team, such people said. But that's only if they can work as a team and take advantage of Microsoft's technology and raw financial power and Yahoo's attractive content.

"To make this really sing, you've got to have a person at the helm who's a truly visionary leader," said Gartner Group analyst Allen Weiner. "I don't see that person at either company right now."

One item on the leadership agenda might be getting Microsoft to swallow some pride and admit that some of its offerings are less compelling than those of its intended partner, Weiner and other experts said.

If the two companies' search and news-aggregation functions were integrated under one name, the result might be a boost for Yahoo's brand -- with its more popular array of sports, weather, business and entertainment sites -- at the expense of those bearing Microsoft's MSN and "Live" monikers.

In any event, the advertising community will be rooting for the deal to close because it fears the increasing dominance of Google in the online paid search category, where it has about two-thirds of the market.

"A lot of people want an alternative to Google," Standard & Poor analyst Scott Kessler said.

Simply adding Microsoft's and Yahoo's shares together doesn't make them more formidable in the paid search arena. That will take the kind of joint research-and-development innovation that Microsoft's Steve Ballmer said he expected from the proposed merger. But combining the two companies should help block Google's inroads into online display advertising, where it trails Yahoo and Microsoft, as well as Time Warner Inc.'s AOL unit.

And what of AOL?

Time Warner's new chief executive, Jeffrey Bewkes, came into that job just last month under pressure to streamline the company and focus on its core news and entertainment brands. That means divesting its remaining stake in Time Warner Cable, most analysts say, and it also may mean finally cutting AOL loose eight years after one of the media industry's biggest merger flops.