In a Book called "Habit" which deals with habit as main behavior driver of consumers the author makes the following point:
Since 95% of behavior is gouverned by habit ads are and should be designed to reinforce habitual behaviors. In other words: you don't do ads to alter attitudes or improve "images" but to implement or more often rather to reinforce brand related habits. If a brand doesn't "own" such habitual behaviors - too bad. A brand should own them he says.
Now, we rather assume that ads are for news and CRM is for retention. This guy says ads are rather for retention (since habits as such are for retention)
It's an interesting point,don't you think?