Pretty much everyone owns a cell phone these days, and with the great advantages of cell phones also comes responsibility. There is certainly proper and improper cell phone etiquette, and unfortunately, improper cell phone etiquette is still rampant amongst the general population.
One prime example of bad cell phone etiquette is people yelling into their cell phones. Have you ever noticed how people talk much louder into the cell phone than a regular phone? It's very common, and can be extremely annoying for all those nearby. A lot of people will excuse themselves into another room when taking a call, but there are some times when you can't leave. For example, when you're riding in a car with someone, you might need to take a call, and there's no "other room" you can go into. It is times like these when cell phone etiquette is of the utmost importance.