1. Is it reasonable for photo journalists to try and get intimate photos of celebrities?
It's probably not "reasonable" by the standards of your average person. The business of finding out celebrity news in all its forms, however, is far from a reasonable business. As with other journalists, photographers have to go after the news. While looking for any sort of dirt on celebrities might seem like tabloid fodder, it's news because it generates interest among millions of people. The fact that celebrity scandals are more enticing to millions of people around the world than the state of world politics doesn't invalidate what the reporter is doing. If nobody gave a crap about Kate Middleton, then there wouldn't be an issue.
2. Is there a difference between a photographer taking a photo of Kate Middleton from miles away, but on public land, to somebody leaking the photos off Scarlett Johansson's phone or whatever?
It's something of a low thing to do, no matter how you slice it. Again, however, this is the kind of stuff that millions of people want to know about. Because they want to know about it, you have well known publications willing to pay big money for stuff like nude photos of popular celebrities. While it's usually the photographers that often get all the crap, it's the tabloids and other publications that ultimately create situations. For instance, let's say you're a photographer that's and about and you happen to see a popular celebrity right now. Say..I dunno...say Emma Watson from the Harry Potter movies. You follow her around for a while, at a distance, taking pictures and you suddenly get a picture of her taking her top off. You start to get excited because you've come across a huge scoop in terms of celebrity news. You've got topless pictures of a hot Hollywood starlet that's been one of the primary characters in one of the biggest franchises of all time. You know why you're excited? Because these pictures will not only make your reputation but will start a major bidding war by every major tabloid publication out there. With these one set of pictures, you could be looking at a six figure payday. With such high stakes that've ultimately been created by publications willing to pay massive sums of money for exactly these sorts of shots, it's hard to blame someone for not going for it. In a lot of ways, you gain an opportunity to advance yourself at the expense of others. It's not always pretty, but neither is life. Sure it also has something of a scummy feel about it. At the same time, it's easy to justify such actions to yourself. Some could argue that it's no less scummy than pro athletes making tens of millions of dollars a year playing games ultimately created for kids.
3. Is it morally ok to look at the photos of celebrities that they haven't intended to go public?
While I do believe that there should be boundaries that people shouldn't cross, you sometimes have to wonder how many of these photos or videos were actually "leaked". Today especially, thanks to the internet and reality television, it takes less talent than ever to be a big star. If you wanted to be famous twenty years ago, you actually had to be able to sing or dance or act or have athletic ability or have a lot of intelligence. These days, all you have to be willing to do is act like an idiot or take nude pictures or make sex tapes that are "leaked" to the press.
As far a the morals for celebrities that legitimately don't intend for things to be leaked, I'd say it's not morally right. I know the concept of doing the decent thing and respecting someone's privacy seems outdated these days, but it really shouldn't be. At the same time, it makes me think of how the game is played and it very much is a game. Celebrities court endless attention when they want something and when it's convenient for them. They can't get enough of the photographers and paparazzi whenever they're on the red carpet or have a movie coming out or a tv show about to debut or a new album about to be released. The rest of the time, however, they believe that the photographers should just go away. For a lot of celebs, it just screams entitlement and part of me does like to see people like that taken down a few pegs. If you're someone that chooses to live your life in the public eye, then there are going to be trade offs. It's foolish and even arrogant to expect otherwise.
While it might be morally wrong, the VAST majority of big success stories among celebrities come about because someone is willing to make the most of an opportunity. For instance, like I said earlier, there are tons of people today that are famous or wealthy without having any real talent other than making a fool of themselves. However, that can lead to major financial gains so, in some ways, I can't blame them for taking advantage of an opportunity when it comes their way. That's how fame & fortune are generally earned. As far as Kate Middleton goes, she had to know what she was getting into. When she first started dating one of the members of Britain's Royal Family and son of the late Princess Diana, she'd have had to be a complete moron not to know what she was getting into. At the same time, I bet she was thinking & seeing dollar signs the first time she went out with her future hubby. Again, this is a gal that saw a huge opportunity and she went for it. That means you have to expect some bad to pop up along with all the good that's going to come about. No matter what, you can't have it all no matter how rich or famous you are. There are always going to be some trade offs and you're kidding yourself if you believe otherwise.