Spotify is an awesome app for the iPhone, however, you need a premium account. Or do you? Most users will probably use the off-line mode to avoid the sometimes overly expensive data plans. If you don’t want or need to stream music it turns out you really don’t need a premium account! At least not one account per device.
I noticed it this morning when I installed the Spotify app on my girlfriends’ iPod touch. I’ve been a premium customers since the launch and my girlfriend has a free invite from my account. While my iPhone was streaming music I logged into the same account on the touch and started offline sync’ing some playlists. The iPhone didn’t even stop streaming! I could off-line sync playlists on both devices at the same time. When i started playing a track on both devices however one got a message about the account being used elsewhere, even though the tracks were offline’ed. So as long as your devices remain unconnected to the net you can share your account with others.
I don’t know if this is intentional by Spotify but you could easily share one premium account with all your friends for iPhone/iPod use. It would be rather simple for Spotify to pair an account with one device but that could potentially annoy some customers. In my opinion that would be reasonable and perhaps they will add some kind of account sharing protection if it’s widely abused.
Happy account sharing while it lasts!