It costs $4 million to run a Super Bowl ad -- and you'll see plenty Sunday. But is it actually worth it?

There's a lot of mediums competing for people's attention in today's world. Even during the Super Bowl when commercials are at a premium, they won't have the full attention of viewers, writes Forbes' Darren Heitner:

Despite the fact that 30-second television advertisements during the Super Bowl sell for approximately $4 million, the game will be streamed online and on smartphones, and many viewers will be staring at their Twitter feeds during breaks in the action, all of the ad space is said to be sold out. Digital continues to grow, as does the cost to advertise on the Super Bowl, yet demand for the coveted 30-second spot has remained. Is there a threat of that changing in the near future?