A few people, such as popeater and gossip cop, are saying the Miley Cyrus naked cell phone pic is not actually Miley, mostly because Miley has "just breathe" tatted under her left breast, which you can't see in the naked picture. But of course this picture was taken in a mirror, so what you're actually seeing is her right breast. It's the ol' titty switch-a-roo. The oldest trick in the book!
Popeater also says her lawyers are gathering to see if they can sue anyone, which they wouldn't bother to do if it wasn't actually her.
Even more conclusive is that she was undeniably at the Westin Palace in Madrid for the Europen MTV Awards Hotel one month ago. Here's a video of her leaving the hotel. And here's a picture of the bathroom floor inside one of the rooms (taken from this page on tripadvisor.com). You can see (here) both pics have identical marble floors.
So is it Miley? The definitive answer is: how the hell would I know. Probably, yes. Because Miley is slutty and this is the kind of thing sluts do. Plus, she was over in Europe, where all the perverts live. There's no rules over there, and you buy opium in vending machines.