Once again, this show is called THE X FACTOR, something Britney has. This show isn't THE VOICE... Britney has the rights to judge the contestants because they're actually looking for someone who has THE X FACTOR, not just a VOICE.
It doesn't really matter if Britney can sing or not. She HAS the X Factor so she's fit to be a judge. It's not necessarily about finding the next amazing voice.. it's about finding the next superstar. Most superstars these days don't have the most amazing voices (), but because of studio magic/good looks/ability to dance () they make it big anyway.
Simon better hide if he does something like this to Brit or Demi
History will show a dark time in our culture in which a million followers on Twitter became a key component to winning a Grammy. But thank God for Pink. While Christina Aguilera has a tendency to oversing, Britney Spears can't sing, and Lauryn Hill sorta stopped singing, Pink has managed to carve a brilliant 13-year-career by being something that is incredibly rare these days -- an artist. A complete artist. - CNN