i dont beleive its legal exactly. and morally its probably not right anyhow. but that doesnt mean it wont continue to happen. im sure theres loopholes with it in the law with alot of other things that occur on the internet that will allow people to continue to do it.
BTW. even secure networks arent secure.. if your running wireless even with encryption your not safe. hell actually mac addresses arent entirely safe since they can be cloned. but thats a little harder to do then break an encryption key. think im ****tying you? google "airsnort" thats the software that allows an encryption key to be decrypted just by testing packets. i never use encyption keys but filter by MAC.