Microsoft has hired Goldman Sachs to help it acquire Yahoo, the New York Post reports today. Writes the paper:

Stung by the loss of Internet advertising firm DoubleClick to Google last month, Microsoft has intensified its pursuit of a deal with Yahoo!, asking the company to re-enter formal negotiations … The new approach follows an offer Microsoft made to acquire Yahoo! a few months ago, sources said. But Yahoo! spurned the advances of the Redmond, Wash.-based software giant. Wall Street sources put a roughly $50 billion price tag on Yahoo!.

Buying Yahoo would represent a hugely risky bet for Microsoft, as both companies have been struggling with the management of their internet businesses, losing search and advertising share to Google. Combining two weak performers rarely produces a strong performer.

Henry Blodget suggests that, should the companies merge, Microsoft should immediately bundle up its Yahoo-MSN web properties and spin them off. That not only seems unlikely (as Blodget notes), but would also undermine the long-term rationale of a merger. For players like Google, Microsoft, and Yahoo, content and services – the media business and the software business – are becoming inextricably intertwined, all the way from the underlying data-center infrastructure to the point of consumption. Microsoft has come to believe, for instance, that advertising will be central to the software business in the future. It’s not going to spin off its ad networks or search functions.

Nevertheless, the odds against such a merger paying off are high. But maybe Microsoft, despite downplaying its rivalry with Google, is starting to feel desperate. And maybe Yahoo is, too.

UPDATE: The Wall Street Journal, following up on the Post report, has more details. It notes the organizational upheavals that might follow a merger:

Top Yahoo executives could be a big obstacle to any deal. Co-founder Jerry Yang, for one, has a reputation for disliking Microsoft and avoids using Microsoft products, says one person familiar with the matter. Top Yahoo staff might leave if Microsoft acquired the company and triggered a vesting of their Yahoo options.

UPDATE: Scott Rosenberg posits that a Microsoft-Yahoo merger would be a replay of the AOL-Time Warner deal, signaling, among other things, an impending market top. Things do seem to be getting frothy out there.