Advertisements are ubiquitous. They're everywhere and there's nowhere to hide from them. They can be seen on virtually everything, such as TVs, magazines, newspapers, buses, billboards, etc. Advertisements are a prime example of classical conditioning, especially higher-order conditioning. By repeatedly pairing their products with certain images and sounds, advertisers are trying to establish classically conditioned connections between their brands and certain emotions.
An example of this is the famous ASPCA ad with Sarah McLachlan, which can be seen here. The commercial displays heartbreaking images of animals in distress while McLachlan's ballad "Angel" plays in the background. The images of the abused animals evoke emotions of sympathy and compassion. The ad is trying to pull at your heartstrings and also your wallet. In the commercial, McLachlan asks viewers to join the ASPCA and to subsequently donate a monthly gift of $18. By using the devastating images of the animals, the ASPCA is trying to "guilt" viewers into donating money to the organization. The commercial portrays the ASPCA as a solution to fighting animal cruelty and the "humane" thing to do is to support their organization.
However, the commercial just seems morally wrong. In a desperate attempt to raise funds, they're exploiting the very animals they're trying to help. They're compelling people to donate, out of a sense of guilt, and I believe that it's a cheap methodology.