While many are preparing for a dark day for Yahoo's share when the market opens on Monday, I don't think the shares will get battered too roughly, although there will be volatility. Microsoft's withdrawing of its offer isn't good news to many, but speculation on what Yahoo may have up its sleeve might keep the stock from slipping too far.
It's possible that Yahoo overplayed its hand, but it's also possible that Yahoo may have had other plans, yet to be revealed. The plans could involve Google, or private equity, or even something far-fetched like Oracle. And in the end, nothing says they can't get back to negotiating with Microsoft. Only this time, they would probably keep it quiet, until a final deal is stuck.