My love-hate relationship with limited video previews of Broadway shows

I know it's a good marketing technique, but I hate that I can't find very much video of new and old Broadway shows. It's all part of equity laws, but it's also a good marketing technique that piques interest and forces the viewer to actually go to the show to see what they want to see.

For example, The Book of Mormon has no video footage of the show available, and How to Succeed in Business Without Really Trying has made an extremely limited amount of video featuring its star, Daniel Radcliffe, available. Radcliffe, also known in Hollywood for playing Harry Potter, is the main star attraction. People go to the show to see him, regardless of whether the show is any good. There has also been a lot of speculation over whether Radcliffe can actually sing, act and talk with an American accent. Therefore, marketers have made very little video of him available, but at same time they have promoted him and used his name to propel the show's success.

What is a reasonable preview of a product?