If I buy a TV show or movie with AppleTV or iTunes, can I download it again later if I delete it?

"In short, not easily but it is possible.

There have been numerous blog postings about people being able to re-download their purchases but it's not something that can be done automatically. You will have to call/contact Apple and get some sort of authorization to do it.

My recommendation is to back your purchases up on another computer and not have to worry about such things."