Milli Vanili lip-synched to someone elses voice because it was before the tuning and other magical capabilities of today. Now anybody can be a singer. Trust me, I know a bunch of 'em.
BTW, speaking of anyone being a pop star...
Get a load of this video :
HOW TO CREATE A SEXY POP STAR. That tells you how technology like a software called AUTOTUNE can make a looker who can’t sing a pop singing sensation :
http://youtube.com/watch?v=irk3_p15RJY