According to an interview with Callie Throne about her role on the upcoming fourth season of Californication, she is going to be topless during a sex scene.

"“For me, it was a dream. Suddenly there was a cut off as to how much I had worry in terms of exposing myself, physically and mentally, because there were these boundaries…Then on Californication, because it’s Showtime, obviously there are no boundaries. They really said it was up to me, and they left it up to me and my comfort factor. They never said, ‘You can’t have this role unless you show your breasts.’ Ergo, I felt comfortable. I did show my breasts. I sort of thought, ‘You know what? I’m not getting any younger and this is a hysterical scene and if I’m laughing through it why not?’ And so it happened.”

http://crushable.com/entertainment/exclusive-rescue-mes-callie-thorne-gets-ready-to-show-some-skin-on-californication/

An insider with connections to Showtime has also posted that Addison Timlin (Cashmere Mafia), who plays the daughter of Callie Thorne's character, apparently will also be topless.

"It's definite. I have my friend who works at Showtime, and even though I haven't been able to get any screeners of this one, the role required nudity, and in fact, much like Callie Thorne said happened to her when she got her gig on the show, the word around the network was that Timlin had to take off her top one of her very first days on set, and that it seemed like no big deal for her. "

The fourth season on Californication premieres some time this fall.