The Hitwise blog has some interesting figures on the Google vs. Yahoo! battle.  Although it leads the world in internet searches, Yahoo! and it's child properties still sit at number one atop the list of most popular websites.  In fact, at the present Google comes in 4th, trailing not only Yahoo!, but also Time Warner and Microsoft/MSN.

Responding to a prediction by Citigroup that Google would take the number one spot by sometime next year, Bill Tancer did his own math and his own research.  Interestingly, his numbers came out a little different.

After combing Yahoo's top 20 web properties and Google's top 20 web properties, Tancer compared the two.  He then applied current growth trends (which, realistically change from month to month) and predicted 2009 as the magic year for Google.  In all likelihood his numbers are off as well.

The fact is that there is no concrete way to predict when or even if the shift will occur.  Yahoo could surprise the world with a surprise tomorrow and we could all but forget the name Google in a year's time.  In the up and down world of technology and the internet, nothing is certain.

A final interesting bit of information from Tancer's analysis are the tables comparing each companies properties to one another.  As Tancer points out, almost 90% of Google's traffic comes to it's web and image search services.  Yahoo, on the other hand, has the majority of it's traffic spread out over a wider variety of services.

Only time will tell how this will play out.  My advice:  don't make any assumptions and don't put all your marketing eggs in one advertising basket.  Things could change in the blink of an eye.