Could you make a crawler that crawled S3? Does it already exist?

We are aiming to handle academic lecture video, slide decks, handouts, class notes, etc. The professors aren't terribly worried about it, but they want to know. I really don't know what S3's security policies are. Any experience with this? Anyone?

On a related note: do use use one-time-use URLs to privatize S3 content? If so, how? Do you reach in and expire the links at the same time as the session cookie expires?