Like other publicly held companies, Yahoo! faces keen competition as well as the market's mercurial opinion as to its stock's value. With some huge hurdles in online advertising, it's joined forces with Zillow.com, but the alliance failed to keep Yahoo!'s stock from sinking 20 percent, a punishment reminiscent of the tech-wreck of 2001.

CBS Marketwatch reporter Bambi Francisco blamed the stock rout on a "disappointing second-quarter results," a weak sales forecast for the current quarter and the delay of its new search-advertising technology.

So far, Yahoo!'s stock has fallen 30 percent this year, says Ms. Francisco, for failure to please "momentum investors who expected Yahoo! to raise it's profit forecast, which it has not done for two quarters."

One reason is there are a lot of places that people can advertise online and they want to go where the searchers are, which is why Google likely "makes more profit from each search query" than Yahoo, according to Ms. Francisco.

That means that Yahoo! has to do whatever it can to bring more people to search on its site, so it can earn better margins on its advertisements sold on search results pages and from its branded advertising from across Yahoo's non-search properties.

Enter Zillow. Like viewing homes for sales, consumers enjoy knowing what their homes are worth, and Zillow.com is among the most popular home-valuation services to consumers.

The Zillow.com branded ad will boost Yahoo! Search with a shortcut that allows users to enter their addresses and that leads them to a valuation page where similar homes are featured on an interactive map. Consumers can zoom in to see their neighborhood, its surroundings and other homes.

The Zillow valuation service can also be accessed on Yahoo! Real Estate by clicking on the "What's My Home Worth?" button.

The Yahoo! Real Estate Home page is now loaded with branded advertising including loans from ditech, find a Realtor from HomeGain and find a home or rental from Prudential. Now the search engine site will include home valuations from Zillow, which has its own advertising platform, a partnership with LendingTree and mortgage rates from Bankrate. In addition, the site sells advertising spots to real estate agents.

So what's the point of this story?

None of these sites can do it all for the consumer in one place without handing off the consumer off to an advertising partner, and that's why there's always room to add one more. Yahoo! isn't necessarily the best place to search for homes, get a loan, or get a home valuation because its job as a portal means it doesn't have to excel in every category. All it has to do is provide interest to Internet searchers who will find out on their own who's good and who's not.

Zillow will boost Yahoo!, but only in the short term, until another website comes along that provides better, more accurate home valuations. Consumers will find that the home search on Prudential's ad doesn't have all the listings. What they won't know is that there may be a problem with noncooperation among IDX site owners in which other brokers may not allow Prudential to use their listings in certain areas. A consumer could conclude that Yahoo! isn't the best place to search for homes, find a Realtor, or get a loan.

And then it will be right back where it was -- fighting for its life against a competitor who does it better (and free, for listings) -- until someone else comes along.