Not only is there no need to rinse or wash beef, pork, lamb, chicken, or veal before cooking it, says the USDA's Food Safety and Inspection Service, but cooks who do increase the risk of cross-contamination. Any bacteria lurking on meat when it comes out of the package will die during cooking. Sadly, you can't say the same for your sink, counters, utensils, or cutting board, all of which should be washed with hot, soapy water, rinsed, and then air- or paper-towel-dried after being in contact with meat.
Another reason not to rinse: Excess moisture on meat's surface thwarts the Maillard reaction, the intricate chemical process that occurs when carbohydrate molecules react with amino acids, yielding the coveted sear on that steak. The interchange between the two produces hundreds of different chemicals, explains Harold McGee in his book On Food and Cooking: "pyrroles, pyridines, pyrazines, thiophenes, thiazoles, and oxazoles," which give a brown color to the meat along with rich, complex flavors. The Maillard reaction begins at approximately 230 degrees Fahrenheit. Water, which turns to vapor at 212 degrees Fahrenheit, simply won't get hot enough to allow the Maillard reaction to occur. That means a watery piece of meat won't start browning until all the water is cooked off, but by that time your T-bone might already be well done.
So no, don't rinse meat. In fact, once you lift it out of the butcher paper or wrench it from the shrink-wrap, you should dry off any existing moisture carefully with paper towels before putting it in the pan to brown. Then throw the towels away. And wash your hands really, really well, for a full 10 seconds. Remember?