While much of the analysis surrounding Microsoft's bid for Yahoo remains focused on the PC-based search and web applications markets, the eventual prize in play for these portal firms could be the mobile Internet, experts say.

"Microsoft and Yahoo both have assets in the mobile arena that complement each other very well," said John Delaney, principal analyst at Ovum. "The big portal players all have strengths and weaknesses in the mobile arena, but none of them have it all."

The emerging mobile Internet market will eventually surpass the PC-based Internet market for the obvious reason that there are far more cell phones in the global market than there are PCs. There are close to 4 billion cell phones globally and about 800 million PCs.

"The mobile Internet is not top of Microsoft's or Yahoo's minds in making this deal but it is an interesting angle," Mr. Delaney said.

While Google, Microsoft, and Yahoo have all made significant inroads into the mobile market, none has achieved a dominant position in the emerging market.

Microsoft has acquired a significant position through its Windows Mobile operating system and Yahoo has a number of personal productivity and entertainment applications such as email that are popular in the mobile sphere. Yahoo also has a long track record of partnerships with mobile operators including AT&T, Verizon, and Vodafone.

Google on the other hand has has been very active in recent months boosting its position in the mobile market.

The search king, a major proponent of open mobile networks, is currently involved in the 700 MHz auction in the United States.  The Mountain View-based firm has also introduced its own mobile device operating system, Android, and has fine-tuned its applications for mobile communications.

Google has also forged partnerships with a number of carriers including T-Mobile and Sprint Nextel, and high profile players such as Apple.

"Google's mapping and search applications fit very nicely in the mobile market and while Microsoft has made its mark, it has not captured the imagination," said Joe Nordgaard, director of wireless consulting firm Spectral Advantage.

There is much more competitive balance among the Internet portal firms in the mobile market than there is in the PC web applications market where Google dominates for the most part, he said.

Today the mobile advertising market generates about 1 percent of the overall global expenditure on advertising, but that is expected to grow rapidly over the next few years, according to many projections.