Especially if the music is unreleased.
If everyone is digging some mix from a party, and the tunes they really dig are unreleased, you end up with this big buzz about these tracks nobody can get hold of.
Which not only creates good promotion for the tracks for when they are released, but also generates buzz around the DJ playing them.
So who doesn`t benefit here?
Tenaglia is tied up with major label interests though, the same interests who are shitting themselves over the market change, and will do anything to stop free distribution of music, for profit or not.
One of the cool things about the dance scene was it`s independance and feeling of rebellion against the corporate drollness of everything.
The superstar corporate DJ killed this.