Jeffrey Morgenthaler demonstrates the differences between shaking and stirring cocktails, as well as when you should use which method.
Bonus points to the commenter who can tell us all why James Bond is, shall we say, wrong in his request to have his vodka martini shaken.
A Jigger of Blog 
Clearly because he is ordering a martini with vodka instead of gin.
By: Jeff Fulcher on March 20, 2009
at 11:44 am
Shaken martinis are better able to deactivate or neutralize peroxide than stirred martinis.
http://www.bmj.com/cgi/content/full/319/7225/1600?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=stirred&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
By: Joe on March 20, 2009
at 1:08 pm
Because he likes loose women and weak drinks.
By: Austin on March 21, 2009
at 8:34 am
Good answers…Bond usually explains that stirring bruises the cocktail, which while technically true is not correct as distinguishing from shaking. Bruising is the act of water melting into a cocktail and diluting it. Bruising is a natural part of any cocktail and both shaking and stirring succeed in bruising a drink. Bond implies that the presence of a foreign object, the spoon, does more than shake. But shaking requires a shorter duration to receive comparable amounts of melting. That said, shaking also is more violent and is more likely to produce ice shards in the drink. This is not desirable in a spirits-only cocktail like a Martini.
Plus he ordered it with vodka.
By: Matt Hamlin on March 23, 2009
at 12:27 pm