They've been going on for years.
They had a mad one a couple of years ago which they held on one of the uninhabited island near San An. They ran out of water after a few hours and had to rely on Vodka to see them through the rest of the night.
Your best bet is trying some of the markets or beaches where the travellers hang out. You won't have much joy in the usual bars/clubs, believe me , I've been trying for years to attend one.
I heard there were supposed to be beach parties at Jockey Club @ Cala Jondal after Space on a Sunday but when I drove down that lane last year to get to it the place was deserted. I was gutted as theyre supposed to be unreal. Anyone know if Jockey Club are doing them this year??
there used to be this fullmoonparties in cala youndal, but i think since 2 years they are forbidden (big clubs mafia)....there also where parties in benirras....but i think they are also history....ask in ibiza town on full moon days, maybe they know private parties