Why You Should Never, Ever Shake Your Martini

Information that is chilling - and stirring. JL

Cynthia Graber and Nicola Twilley report in Mother Jones:

Typically, when you shake a drink, it will get colder—and thus more diluted—than it would be after stirring. Shaking also adds texture to a drink, in the form of lots of tiny air bubbles. That's good when you're making a cocktail with ingredients that taste nice foamy, like dairy or fruit juice, and not as good when you're mixing straight liquor with bitters.
Whether you sip it with friends, chug it before hitting the dance floor, or take it as a post-work pick-me-up, there's clearly nothing like a cocktail for bracing the spirit. In addition to its peculiar history as a medicinal tonic, plenty of hard science lies behind the perfect cocktail, from the relationship between taste perception and temperature to the all-important decision of whether to shake or stir. Shake daiquiris, not martinis. James Bond is famous—some might say notorious—for preferring his martini shaken, not stirred. But science-minded bartenders would urge you not to follow his lead—though quick to point out that the right way to make a drink is the way it tastes good to you. Still, there's some solid science behind why a martini should be stirred and a daiquiri shaken, rather than the other way around. Both methods chill, dilute, and blend your drink—but they have different effects on flavor and texture that work better with some cocktail recipes than others.
Typically, when you shake a drink, it will get colder—and thus more diluted—than it would be after stirring. Banging ice rapidly around inside a shaking tin is the most turbulent, efficient, and effective manual chilling/dilution technique we drink makers use. Because flavor perception, and sweetness, in particular, is blunted at cooler temperatures, a shaken drink needs to start out significantly sweeter than its stirred equivalent.
Shaking also adds texture to a drink, in the form of lots of tiny air bubbles. That's a good thing when you're making a cocktail with ingredients that taste nice when they're foamy, like egg whites, dairy, and even fruit juice, and not as good when you're mixing straight liquor with bitters. Sorry, Mr. Bond.
Or, as President Jed Bartlet put it, "James is ordering a weak martini and being snooty about it."
The other thing to bear in mind is that you really shouldn't linger over a shaken drink. The minute that someone hands you a shaken drink, it is dying. I hate it when people don't drink their shaken drink right away. We can't responsibly advise you to chug them, so we recommend making your shaken drinks small, so that you can polish them off before the bubbles burst.