If a celebrity /wants/ to draw attention to themselves by running around naked, they can. You're perfectly free to say "That's silly, and doesn't impress me.", you're free to spend some quality time in the bathroom, you're free to think they're cool, or think they're idiots.
Personally, I usually judge by how relevant the nudity is. I saw a campaign that took topless pictures of women who had had mastectomys in order to say "Hey, you don't need to be ashamed of your body now" and I think that was a very well done campaign. I'm okay with Kiera's shoot because using her body to make a point about her body seems fair. I'm less impressed with the PETA campaigns, because any connection I can draw between eating a hamburger and a woman's body is kinda insulting really. I'm not a huge fan of "Here's some tits, now lets talk about investment futures in an uncertain market!"
However, ultimately, I don't expect that there are many actresses who care whether or not they impress me personally. They're not obligated to, nor am I obligated to care about the things they want to draw attention to.