Letting a wine "breathe" (letting wine react with oxygen) can be helpful by making some young, tight red wines more relaxed. Unfortunately, simply pulling the cork won't do the trick. Even after sitting open for 24 hrs. there is still not as much oxygen in a bottle of wine as there would be if you simply swirled the wine in your glass for a minute. The other option is to have the wine poured into a decanter or carafe.

To answer this you must ask "what is flavor?". I like to use the very basic idea that flavor is the reaction of an organic compound on your senses that causes a unique sensation in your mind. You can tell the taste of a raspberry when you eat one because it has a unique set of organic compounds that your mind associates with the experience of eating a raspberry.
Wine is a great imitator. Wine grapes have the highest amounts of organic compounds of any fruit or vegetable ever grown by human beings in history. We have only even vaguely identified maybe 5-10% of all of the organic compounds in wine. These organic compounds either duplicate or mimic the same organic compounds found in other fruits, vegetables, flowers etc. Therefore when you drink a wine and taste raspberries what you are really tasting is an organic compound in the wine that is the same as (or similar too) the organic compound that your mind associates with eating raspberries. That is one reason why everyone gets something slightly different out of the same glass of wine. Everyone's tongue picks slightly different organic compounds out of the thousands available and therefore everyone tastes something slightly different.

Because it kicks ass! Oh, yeah. It also has been shown to reduce the risk of certain cancers, heart disease and other major health problems while improving most meals and your quality of life!

The answer to the first question is that wines can turn to vinegar because of a bacteria called acetobacter. These Acetic bacteria can form a film on the top of wines and, when given an ample supply of oxygen, slowly turn the alcohol from wine into Acetic Acid (vinegar). Since this process requires a great deal of oxygen, you will usually only see problems with Acetic Acid in bottles that have leaked or in open containers.

Since the Acetobacter live on the surface of the wine the top of the barrel will be affected first. However, since Acetic Acid is very volitile, it spreads quite quickly to the entire barrel.

During normal winemaking grapes are brought in mostly whole from the field, crushed to release the sugars and inoculated with yeast. The yeast digests the sugar and forms CO2 and Ethanol alcohol. Alternately, if you do not crush the grapes immediately, but instead, leave the skins intact and place the grapes in an oxygen-free environment, then another enzymatic process is initiated within each individual berry as the grapes undergo cellular respiration. This process is known as Carbonic Maceration.
Carbonic Maceration is a way to convert sugar into alcohol without the use of yeast. When the whole clusters are removed from the vine they are still alive but in order to continue functioning they must release enzymes to convert the sugars within the grapes into life-sustaining CO2 and Ethanol (along with a wide range of assorted other organic compounds). This process continues until the alcohol reaches toxic levels for the grape, around 1.5 -2.5% afterwhich conventional fermentation continues until dryness.
This process has a great many implications for a winemaker. Even though this process continues for only the first part of the complete fermentation, this unique process leaves an unmistakably unique mark on the wine produced. The alcohol of the resulting wine will be lower because the initial enzymatic conversion is less efficient at converting sugar into alcohol than the normal yeast-driven fermentation. The pH of the wine will be higher because of the much greater metabolizing of malic acid involved with Carbonic Maceration. The glycerol levels of the wine will be significantly higher which will lead to slightly increased perceptions of sweetness and, at higher levels, a greater sense of viscosity. In addition, the great amount of organic compounds released during the carbonic maceration give the wine an unmistakably delicate, floral bouquet and will add a unique layer of delicacy to the wine. The end result is a wine with bright coloring, an intriguingly complex nose and a delicious flavor driven by forward, fresh fruit.

Sugar Decreases 20%
Alcohol Increases 2%
Malic Acid Decreases 50%
PH Increases .25