Fresh from forcing a reorganization at Motorola, Carl Icahn is now reportedly giving serious thought to trying to replace Yahoo's current board of directors, and engineering a deal with Microsoft.

Billionaire "activist" investor Carl Icahn has been busily buying up Yahoo shares over the past week, and he is interested in waging a proxy fight to elect a new board that would bring Yahoo and Microsoft back to the negotiating tablet, according to an article in Reuters which cites unnamed sources.

However, a decision to offer a proxy slate must be made by this Thursday, in order for the stage to be set for a proxy battle in time for Yahoo's annual meeting on July 3.

Although the chances that Icahn will try to get a new board elected are high, Yahoo isn't likely to cave in easily, say some financial analysts.

"With the deadline to submit a new slate of directors approaching fast and the specter of an activist shareholder hovering over their heads, Yahoo is likely to try to play its best hand yet to derail any attempt to sell the company," said Youssef H. Squali, an analyst at Jefferies & Co., in a note to clients.

But so far, Yahoo has been running a very sharp game in its attempts to ward off takeover bids by Microsoft. As previously reported in BetaNews, in the face of earlier threats by Microsoft to wage its own proxy battle at Yahoo, Yahoo CEO Jerry Yang and his current board have stayed adamant in their resistance to Microsoft.

In December 2007, more than two months before Microsoft first launched its acquisition attempt, Yang presented Yahoo's current board members with a "three-year plan" for remaining independent by nearly doubling the company's operating cash flow and generating $8.8 billion in revenue in 2010. Then on February 13, Yahoo mailed a letter a letter to shareholders aimed at directly fending off a takeover by Microsoft.

"Our goal is to grow visits to key Yahoo starting points and properties, where users enter the Internet, by 15% per year over the next several years. We are the most visited site in the US, and we continue to grow -- we experienced double-digit growth in US users in 2007 on our Yahoo.com home page," Yang wrote in his letter.

Earlier this month, Microsoft abandoned its attempts to buy Yahoo -- for the time being, at least -- after Yahoo turned down an offer to raise the purchase price to $33 per share, or $47.5 billion. Yahoo wanted $37 per share.

All along the way, Yahoo has also defied the predictions of most analysts. In a poll released by Reuters in mid-March, conducted before Yahoo's three-year plan became publicly known, all eight Microsoft analysts surveyed said they thought Microsoft would prevail in its takeover attempt. So, too, did 14 of the 15 Yahoo analysts surveyed.

Yet Icahn has now entered the Yahoo fray at the request of some unhappy Yahoo shareholders, according to an account in the Wall Street Journal.

Icahn -- a veteran of many other directorship battles -- could be very tough to tangle with on the proxy floor. After almost winning a proxy fight at Motorola a year ago, he managed to gain two seats on Motorola's board of directors anyway.

Meanwhile, Icahn leveraged his influence as majority shareholder at Motorola to push a reorganization that has split off consumer products such as mobile phones into a separate division.

Aside from Icahn, other activist investors might also get involved in a Yahoo battle, including Scott Galloway -- a professor at New York University's Stern School of Business -- and his investment firm Firebrand Partners LLC, according to the WSJ report, which also cited unnamed sources.

Icahn is also reportedly supporting a plan by video-store chain Blockbuster Inc. to purchase Circuit City, although he has said that he will buy Circuit City himself if Blockbuster can't get the needed financing.