Starbucks CEO to Retire, Shares Fall  LOS ANGELES (Reuters) - Starbucks Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=SBUX.O target=/stocks/quickinfo/fullquote"&gt;SBUX.O&lt;/A&gt; on Tuesday  said its chief executive, Orin Smith, will retire next year,  surprising investors, who sent the coffee shop chain's shares  lower in after-hours trading.