12 Causes of Advertising Failure:

1. The desire for instant gratification.  The ad that creates enough urgency to cause people to respond immediately is the most likely to be forgotten immediately once the offer expires.  Such ads are of little use in establishing the advertiser’s identity in the mind of the consumer.
2. Trying to reach more people than the budget will allow.  For a media mix to be effective, each element in the mix must have enough repetition to establish retention in the mind of the prospect.   Too often, however, the result of the media mix is too many people reached without enough repetition.  Will you reach 100% of the people and persuade them 10% of the way?  Or will you reach 10% of the people and persuade them 100% of the way?  The cost is the same.
3. Assuming the business owner knows best.  The business owner is uniquely unqualified to see his company or product objectively.  Too much product knowledge leads him to answer questions no one is asking.  He’s on the inside looking out, trying to describe himself to a person on the outside looking in.  It’s hard to read the label when you’re inside the bottle.
4. Unsubstantiated claims.   Advertisers often claim to have what the customer wants, such as “highest quality at the lowest price,” but fail to offer any evidence.  An unsubstantiated claim is nothing more than a cliché the prospect is tired of hearing.  You must prove what you say in every ad.  Do your ads give the prospect new information?  Do they provide a new prospective?  If not, be prepared to be disappointed with the results.
5. Improper use of passive media.  Nonintrusive media such as newspapers and yellow pages, tend to reach only buyers who are actively looking for the product.  They are poor at reaching prospects before their need arises, so their not much use for planting a reticular activator or creating a predisposition toward your company.  The patient, consistent use of intrusive media such as radio and television, will win the heart of the customer before she’s in the market for the product.  Tel her Why; wait for when.
6. Creating ads instead of campaigns.  It is foolish to believe a single ad can ever tell the entire story.  The most effective, persuasive, and memorable ads are those most like a rhinoceros: they make a single point powerfully.  An advertiser with seventeen different things to say should commit to a campaign of at least seventeen different ads, repeating each ad enough to stick in the prospects mind.
7. Obedience to unwritten rules.  For some insane reason, advertisers want their ads to look and sound like ads.  Why?
8. Late-week schedules.  Advertisers justify their obsession with Thursday and Friday advertising by saying, “We need to reach the customer just before she goes shopping.”  Why do these advertisers choose to compete for the customer’s attention each Thursday and Friday when they could have a nice, quite chat all alone with her on Sunday, Monday, and Tuesday?
9. Overconfidence in qualitative targeting.  Many advertisers and media professionals grossly overestimate the importance of audience quality.  In reality, saying the wrong thing had killed far more ad campaigns than reaching the wrong people.  It’s amazing how many people become “the right people” when your saying the right thing.
10. Event-driven marketing.  A special event should be judged only by its ability to help you more clearly define your market position and substantiate your claims.  If one percent of the people who hear your ad for a special event choose to come, you will be in desperate need of a traffic cop and a bus to shuttle people from distant parking lots.  Yet your real investment will be in the 99 percent who did not come!  What did your ad say to them?
11. Great production without great copy.  Too many ads today are creative without being persuasive.  Slick, clever, funny, creative and different are poor substitutes for informative, believable, memorable, and persuasive.
12. Confusing reactions with results.  The goal of advertising is to create a clear awareness of your company and its unique selling proposition.  Unfortunately most advertisers evaluate their ads by the comments they hear from people around them.  When we mistake mere response for results, we create attention-getting ads that say absolutely nothing.   

 Source: Roy H. Williams, “The Wizard of Ads”