it worked in playa d'en bossa, where several thousands of people up for a party are in close proximity and could simply walk down the beach to beachouse.
I might be wrong, but I think they are aware that it's not going to be that easy for them to get the hordes to RUMORS now. so I believe the fact they've announced sunday's guest and generally have given a preview about who's gonna play is part of tactics. if rumors keep going as well as it did at beachouse, they'll stop announcing the guest and will probably also start charging entry at some point. I have no insider knowledge here, this is just pure guessing.