It actually makes no difference whether your martini is shaken or stirred; it's going to taste the same either way. Note: see below for a retraction.

If you think about it, this makes James Bond kind of an idiot -- the bartenders are rolling their eyes behind his back as soon as the camera pans away.


Update: Apparently I'm wrong and there is a difference between a shaken or stirred martini (thanks to Footprints for correcting me). In addition to the decanting/not decanting distinction, shaking a martini can, apparently, bruise the gin and make it cloudy.

On the plus side, according to a Canadian study, a shaken martini may contain more antioxidants than a stirred one. This could be why Bond doesn't have cancer after all these years of hanging out in smoky casinos.

However... I maintain Bond is an idiot. First off, a real martini is always made with gin, not vodka (as 007 orders it). And secondly, according to some, when you shake a martini instead of stirring it's not a martini anymore; it's a drink called a "Bradford."