A skunk’s odor can be detected by humans as far as 1 mile (1.6 km) away. When a skunk feels threatened, it sprays an odorous fluid from its anus. The odor is not dangerous, but it is extremely pungent. Skunks can spray as far as 18 feet (5.5 m) if it is carried by the wind, although an average spray travels about 12 feet (3.6 m) with accuracy. The scent of a skunk’s spray on a surface typically goes away after two to four months without action, but applying acidic items, such as tomato juice or diluted vinegar, to the surface will offset the scent of the skunk's highly alkaline spray.
More about skunks:
I've always found skunks to be one of those animals that immediately alert anyone who sees them, myself included.
Those black and white colors are definitely a sheer warning to stay away from them. Unfortunately though, some have to learn the hard way.
While I can't say that I've had a bad encounter with a skunk, I have known owners whose dogs have been sprayed, which doesn't really surprise me, as it's also mentioned in the third bullet point as well.
Also, while it's true that dogs can get sprayed for ignoring the warnings of a skunk, another possible reason is because they're outside quite a bit, especially at night.
I remember one time a few years ago, where one of my neighbors dogs was sprayed by a skunk, because he/she was out way too late at night and tried to attack it. Perhaps the best solution to this, is to bring them inside early, so that they don't have any close encounters.