Years ago there was a local used record store in my town that offered a "trial" period on any album purchased. If you "didn't like" the album you could return it for a small "restocking" fee. Unsurprisingly this store also had a good business in the sale of blank cassette tapes.
What prevents someone from doing the same thing with Spotify? Play music on one device, record it on another using audio patch cables if needed. Or maybe it isn't even that hard, just record the audio signal right out of the audio card in your PC. Is this prevented somehow?
It's not prevented. You don't even need to go that far -- there are programs that will get the ogg files directly from Spotify. I'm not going to link to them, but I trust you'll find one with sufficient google-fu.
What prevents someone from doing the same thing with Spotify? Play music on one device, record it on another using audio patch cables if needed. Or maybe it isn't even that hard, just record the audio signal right out of the audio card in your PC. Is this prevented somehow?