If you have been following the Yahoo-Microsoft merger discussions as closely as I have, you will not be surprised that the deal fell through.  Skipping the personalities involved, the financial terms and strategic fit, I felt that the deal would not go through for one simple reason -- time.

Typically, deals that get consummated are those that are negotiated and closed quickly.  If a deal takes a long time to develop, it usually never gets done even if it makes the most sense.  As time passes, people start to question the business terms and thought process involved.  People start to crawl out of the woodwork to question the deal. 

As a result, the negatives on a deal continue to build over time while positives stay constant (or decline). 

Looking back to the Yahoo-Microsoft discussions, one of Microsoft's biggest mistakes was to allow the discussions to evolve slowly overtime.  If they pushed the discussions harder and faster, they would have had a better chance to reach a deal with Yahoo!