Adult Content On Twitter

What's Twitter's stance on adult content? I've see adult content on it before, but it is hard to tell if that is somebody that is going around the rules and getting accounts banned.

It's fine as long as your mark your account as containing sensitive content in profile settings

lots of user actually post nudes there to earn direct links from adnetworks.

a lot of pornstars/camgirls have twitter accs and they're often posting explicit content

here's a few guidelines by twitter regarding to adult content:

"...using common sense won't steer you wrong. If you upload media that might be considered sensitive content such as nudity, violence, or medical procedures, you should consider applying the account setting "Mark my media as containing sensitive content". "
"Graphic Content: You may not use pornographic or excessively violent media in your profile image, header image, or background image."

and here's a pretty fresh article about twitter's viewpoint of nonconsensual adult content aka revenge porn:
draw your own conclusions