I'm not being narrow-minded, but here are my thoughts.
How can you look at some photos and "know" which are ghosts and which are not? How can you know? Are you saying when you see special effect ghosts in films there's a possibility they are ghosts too? Anyone could Photoshop an image and make it look like there's a ghost. It isn't hard, and you guys have fallen for it.
That picture has a faint outline of a face in the bit of fog. Wow! Amazing. Do you know that the human brain will believe whatever it wants? I could barely even see it at first, but when you look hard enough you see 3 darker areas which slightly resemble a face. Wow, that's so unlikely.
Currently the only limit we have is science. If this limit is broken, there is no limit to what can happen. What stops us from flying, or from making objects move, etc.? You can believe what you want, but that doesn't make it exist.
There may be unexplicable things, but do you realise most of those are based on what people believe they've experienced? Come on, anyone can see a TV turn on and think it's a ghost. Hello? Dodgy wiring? Oh my, I just saw something in the sky, it must be a UFO because there's nothing else it could be!
I know most of the people who "believe" are going to shrug this post off as narrow-minded or something, but you have to understand I'm not saying you can't believe in it, I'm saying you need to think things through and not shrug off scientific explanations for your "ghost" theories since right now it explains pretty much 99.9% of what happens in your life. What is doesn't explain is simple - the human brain. The human brain is what "creates" ghosts. Think about it.
What's more, people arguing over it makes it even less credible. They're either visible or not, they can either be photographed, or they cannot.
* segosa realises he's most likely pissed off a few people. 
