Netscape and Ning cofounder Marc Andreessen needs 1,800 words to say that what's really holding up the Microsoft-Yahoo merger: fears that they could strike a deal, but then see it collapse. Here's the 100-word version.

A deal could be negotiated and announced and then fail to close. Mergers can take a year or more. During that year plus, the US government could disallow the merger.The EU is currently harsher. Microsoft shareholders could revolt. The broader economy could cave. Microsoft could get cold feet. If the deal is signed and collapses, Yahoo would be disorganized, fragmented, and demoralized. To offset these concerns Microsoft could point all of its users at Yahoo Search, and so on for all of the various overlapping product lines. Yahoo would of course share revenue with Microsoft in return. The Bush administration is known to be quite friendly to large companies, large mergers, and Microsoft. Any Democratic administration would be more hostile.

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