Infrared! LOL!

On another note, if the kids are looking to download as a way to save $.99, I'd call that unethical and discourage them.

If they are browsing to see what they like, watch their buying habits. Encourage them to buy the stuff they like. One of my kids likes movies, and has developed quite a collection of DVD's. It seems she uses filesharing to browse for movies, and then a few weeks later the DVD's arrive in the mail. So, her use seems ethical to me. She's buying more (often as gifts for friends) than she would before she started using filesharing.

There have been reports that filesharing helps sales, and watching what the kids buy, I'd say that is true.

So, while the legalities are unclear, the ethics seem simpler and easier to encourage.