Here's a newsflash...
Frequency is important in advertising.
In a new study by Nielsen published in something called Mobile Commerce Daily, ad recall and purchase intent increased when people saw an ad on their smart phone and tablet as well as on TV compared to people who just saw one :15 second ad on TV.
Even though the new digital evangelists would like you to believe this compounding effect is a new phenomenon created by the brilliance of mobile platforms, this is how advertising has always worked.
In the olden days before these magical devices, we put ads on television and radio, and newspapers or other relevant media to increase reach and frequency. Over the years as advertising media has evolved, the principles haven't.
The goal has always been to reach people with a relevant message at the times and places that have the most impact.
While new technology makes this easier and hopefully more effective than ever, what isn't new is the principle behind the behavior.
It's not rocket science. It's advertising.