Nothing happens if someone drinks spoiled wine, since wine can't really spoil; the alcohol acts as a preservative. When wine is built for aging and stored properly, it can taste delicious in spite of its age. If it has not aged well, it is still acceptable to drink, but may taste bad or even like vinegar.
When wine is old, it may be less fruity and more nutty in flavor. It may also take on a brown color. It is important to note that this can happen to many wines, since most are not meant to age. White Zinfandels, for example, were meant to be consumed immediately while fine Bordeaux wine is meant to age.