There was a time when when you could leave your house unlocked and know no one would enter and steal your possessions. Things change and now most of us lock our houses to protect our possessions.
There was a time when you could leave your car unlocked on the street and know it would still be there when you got back. Things change and now you not only lock your car, you install an alarm.
There was a time when you could post a photo on your blog and know no one would steal it. Things change and now you need to protect your images from the thieves. It doesn't matter how much you bitch about it, you won't change the behaviour of the thieves who steal your images. You need to find a way to make it difficult for them to take something that doesn't belong to them.Here are a few links with some suggestions of how you can protect your images.
But as they say the only way to stop an image being used without your permission is not to put it on the internet in the first place.