Of course, it is the Target commercial (and others) that pay for this lovely little online playground we all enjoy so much. That said, running a :15 spot eon every single video (some of which are actually shorter than the commercial itself) may be counter productive from the marketer's standpoint.
Limiting the number of times each user is exposed to the creative can actually increase the amount of time those users spend watching the creative itself. In other words, if I were running the bingo here (which I am not) I might try and sacrifice the total number of views to try and get people to watch the thing longer and not click away or tone out.
That is ESPECIALLY important when the creative itself is pretty cool, which that ad is. Also, making sure the user is engaged through the entire ad makes a call to action at the end (such as a click through) much more effective.
It would be really interesting to see how much Target's ROI on the ad changed if NS limited the number of times it runs and charged a bit more for each one.