Straw That Stirs The Drink Meaning

(idiomatic, almost always preceded by the) The person who stimulates or inspires a group; the major factor affecting a trend or set of developments.

Example: 1977 May 26, Dave Anderson, "Reggie's woes," Star-News (North Carolina, USA), p. 7D (retrieved 19 Oct 2012):
  Reggie Jackson . . . apparently presumed his charisma would assume command of the clubhouse. . . . " I'm the straw that stirs the drink," Reggie Jackson is quoted by Robert Ward in Sport magazine. "It all comes back to me."
1993 Dec. 7, Jonathan Fuerbringer, "Credit Markets: Bond Prices Continuing to Rally," New York Times (retrieved 19 Oct 2012):
  "We have priced in 4 percent growth in the fourth quarter . . . ," said Alan Levenson, money market economist at UBS Securities. "Growth is the straw that stirs the drink."
2009 Dec. 31, Michael Avila, "Top 10 ‘geek’ movies of the decade," NBC News (retrieved 19 Oct 2012):
  [T]ake a bow, pop culture enthusiasts. You are now the straws that stir the drink. Geeks rule!
2010 March 15, Josh Levine, "The Turbulent Times of Formula One," Time:
  [H]e's still the straw that stirs the drink. Ecclestone alone makes the big TV, sponsorship and track deals that keep F1's cash gushing.