Writing teachers are quick to slash through repetitive, redundant language in their students' essays, and (except in marketing) so are business people.
However, we live in an attention economy, where getting people to focus on a message long enough to comprehend it provides a major challenge. To get someone's attention, the message has to be repeated many times. For example, did you ever count the number of times the radio ad repeats the phone number of the sponsor? Often, it's five times during a 30-second spot.
Redundancy can be even more useful than repetition, because it provides both an extended length of time to allow the message to sink in and alternate language that may get through when the original phrasing did not: "Room and Board included. We will provide a comfortable place to stay and all your meals."
Redundancy goes large when the message is critical: "Warning of fatal shock! You could be killed! Danger of electrocution! Keep ladder well away from overhead power lines. If ladder touches overhead wires, you could receive a fatal electric shock and die." Quibblers will scoff and ask, "So, um, could you receive "a fatal electric shock" and NOT die?" But the lawyers who work for the ladder company will not be budged. (By the way, did you ever count the warning labels on a ladder? One of my ladders has 11 warnings on it.)
Redundancy and/or repetition can be desirable when the information is very important or when the target audience needs reassurance about the fact. So we need to think of the emotional as well as the intellectual needs of the reader.
Finally, thee is the Coca Cola Rule. Why does Coke advertise? Is it to get new customers who have never heard of Coca Cola? "Coke, eh? Hmm. I'll have to try that sometime." Coke's constant repetition, like that of any aggressive brand, is not to provide new information ("Coke? Never heard of it.), but to maintain presence in the overflowing information economy--to reset attention, to remind you. ("Coke? Of course. Haven't had one for a few days. Let's go get a float.")
At a recent visit to the Consumer Electronics Show in Las Vegas, Samsung was all over the place continuing to build its brand image and awareness. The company had painted the entire side of a building with a huge Samsung logo on it, put up banners, attached signs to buses and taxis, printed various cards and brochures, put ads in the show publications, and, of course, had a large booth in the exhibit area.
Finally, in the attention economy, repetition is designed to make familiar the unfamiliar or even the unknown. That's why candidates for office put up signs everywhere with little other than their name on them: "Joe Freen for Congress." If nothing else, they will have name recognition on the ballot when voting time arrives. And we nearly always prefer the familiar or known to the unfamiliar or unknown.
Purposeful redundancy can be a positive practice.