We thought that Youtube was a good gauge of general internet interest in the ad. If you liked the ad or ended up talking about it after, you probably pulled it up on Youtube to see it again.
Youtube views can be and are purchased just the same as TV views. The total views shown on a youtube video is inclusive of paid youtube advertising and isn't a very reliable metric of "interest" (when it comes to ads)
Though, the only real data point that probably matters is what sales were like for the companies. I'd imagine they are at least a little correlated, would be neat to see some actual numbers.
Sales have a longer cycle than these numbers, and while the Superbowl is probably a big enough spend that it's noticeable for some companies, I doubt Budweiser or Nissan saw big bumps in sales from these spots.