Why do producers use alias's?

[alxk]

I recenlty found this Aliases from known Djs that I couldnt believe..

Armin Van Buuren: Amsterdance, Armania, El Guitaro, Gaia, Gimmick, Hyperdrive Inc., Misteri A, Perpetuous Dreamer, Problem Boy, Rising Star, Shoeshine Factory..
Tiesto: Allure, Da Joker, Drumfire, Paradise In Dubs, Tom Ace, Roze, Stray Dog, Tom Ace, Wild Bunch..
Eric Prydz: Cirez D, Moo, Pryda, Sheridan..
etc..

Its a very interesting discussion anw.. I think they dont want us to identify the real artist, or smth like that