Lets remember just some outrageous Britney moments
Britney Spears' most infamous cover / picture of her career (shot while she was underage)
18 years old Britney shocks as she simulates a Striptease on stage at 2000's VMAs
Spears dances with a snake on stage at one of the most PETA's hated performances ever
19 years old Britney shocks with hot music video "I'm a slave 4 U" sweaty revealing britney simbolizes orgies, and her face is licked on a couple of scenes.
Britney Spears kisses Madonna on stage at VMAs 2003.
Britney appears almost naked with one of her most famous outfits of her career in "Toxic" music video.
Nasty Britney Spears licks Snoop Dogg's entire face on the incomplete "Outrageous" music video.
Spears causes controversy at her Onyx hotel tour by simulating sex scenes on stage while kids were present in the audience.
After shaving her head, Britney Spears shocks with the infamous "Gimme More" performance at 07 VMAs, Spears appeared on stage wearing a bikini and a raw haircut as she gave a raw lip-synced performances of the racy "Gimme More".
Spears releases a low-budget trashy and rough music video for "Gimme More" with uncensored leaked scenes.
Vatican critizes Britney and pronounces against her, after she appeared seducing a priest and sitting on his legs on one of "Blackout's" booklet pictures.
Britney Spears uses iluminati / diabolic references on her weird music video "Hold it against me".
Britney joins Rihanna on Stage in a S&M inspired performance during primetime television, generating a bunch of parental complains.
Britney's music video "Criminal" is officialy banned on most countries for being considered as promoting criminal acts, the scenes where Britney uses a gun were panned and caused controversy in UK calling Spears irresponsible and a bad role model for society.
Plus many other moments, not to mention her really controversial acts as a celebrity, and all the elements that most of time were unappropiate for her age.
I think Madonna and Britney are probably the only 2 female popstars that shocked the vatican and obligated them to make declarations and critisism.
Miley just wanted to be sexy for her new twerking music video, and she is watching and learning from "Britney Spears and Madonna", two women she considers didn't play it safe.
The desperation is REAL. 
Say what you want about her image being try-hard and her music being terrible, but she's a highly controversial star. Not to the extent of what Madonna and Britney were in their peak, but her Vanity Fair photoshoot in 2008, "strip dancing" on the ice-cream truck, the entire Can't Be Tamed era, cutting her hair and now the We Can't Stop music video were highly publicized and controversial. She's a mini version of Britney per say when talking about being a risk taker.