I have seen a bunch of these lately as I was researching another alternative to Turtable.fm. Turns out more than half my friends don’t have Spotify so I can’t use it with them. The genius of the old TT was that it (a) had very cute avatars and UX in general and (b) it didn’t require you to pay for a separate service. I wouldn’t mind paying myself that allowed me a certain sized “room” but the moment everyone else must sign up for an external service, let alone a paid one, it becomes a non-starter.
Then charge me as the organizer fir a room of a certain size. But don’t make every one of my guests pay. I am ok creating a virtual DJ space for me and my 30 closest friends. I’m less ok with every one of them having to open up their wallets to sign up for their own subscription even if the amount of money in total is the same.