Have you ever had an experience with a business and said "I'm never buying anything from them again!!". I'm sure you have, in fact everyone has that experience. The reason you feel that way is because they missed your expectations. You thought or believed one thing about the company and they delivered something completely different.
For example, if you go your doctor because you have a severe cold and he tells you to loose 20 pounds and exercise more - you're probably going to be confused. Your expectation was determined by two very important things: (1) you're sick [which was the context for going to the doctor] and (2) you expect him to provide some immediate answers on how to get well. If he does neither - then you'll be a little bent at the doctor.
Another example...you see an advertisement for a new restaurant, the atmosphere looks great, the food looks great, everyone appears to be enjoying themselves. So you go to check it out. When you arrive, you are the only one in the place, it's dark and shabby looking, and the food is terrible [along with the service]. Well your expectation was created by the advertising - they created what ended up being a fantasy. Your context will be much different the next time you see any advertising by them or if you hear their name mentioned in casual conversation. And probably in the meantime, you will tweet, facebook, yelp, urban spoon, etc. them to get your point across - that they did not meet your expectation (in fact, they lied to you through their advertisement).
My point is that as business people, we need to understand the context and support customer expectations as much as possible. Not that you want to say "look, my place is a dump and the food is lousy" - but you might want to lay off the advertising until you get your place spruced up a bit. Set expectations that are just a bit below what you are going to deliver - then you can hit the market and exceed expectations. That's much better than missing.