After cigarette advertising was banned in the UK the tobacco companies reported a rise in profits. It turns out that the advertising didn't actually do a great deal to improve brand recognition but it did cost them a lot of money. Many companies would have liked to stop advertising earlier, but like a screwed up arms race, they couldn't stop running adverts whilst their competitors still ran them.
Do brands like Coke and Pepsi need to advertise? They're two of the most recognisable brand names on the planet, do they actually derive any real benefits from advertising or do they only keep up their advertising levels because their main competitor does the same?
There are companies running adverts who simply do not need advertising. Citrix is a good example. Being in the UK I've not heard Limbaugh's show so I was surprised to hear that Citrix had pulled their adverts from his show. Citrix is a company that everyone who works in IT knows, they simply do not have to advertise to people listening to a radio show to tell people what they do - anyone looking at an IT project that involves virtualisation already knows of them and what they offer. Targeted adverts on tech websites would make sense but a generic radio show? They've quite possibly realised that they weren't getting any benefits from their adverts prior to this incident but needed a good reason to pull their adverts that didn't leave them looking like idiots for placing the adverts during a radio show in the first place.