It has been, but only occasionally. The screen was basically an affordable option, but has limitations such as limited viewing angle for most people. I originally suggested two screens at that end, both on angles, but still not sure that would help enough.
As for its use, it requires a fair bit of effort to put stuff together. Some pre-made (e.g., from TV) ads have been played in the past, but could have limited appeal unless fans are used to looking at the screen for other things - replays, fan close-ups, other stats, etc.
I know that in my usual seats, I only look at it for Fox replays, maybe twice a game, and even then the angle makes it tough to see any detail.
Ideally, would be used for replays (budget option I suggested was having a baseline camera hooked up to a consumer-type harddrive recorder, and have someone operate that), alternative view (e.g., overhead camera), advanced stats (e.g., full stats for one player, cycle through each; or live team stats), feed from a camera that zooms in on the crowd - people cheering, doing silly things, etc.
But all of those things need operators to do properly. Plus the more things that can go wrong, will go wrong.