I understand your feeling, but it is like this, the picture aren't stored on this site, but rather on places like imgur or photobucket. If the person who placed the pictures on that site deletes the pictures or closes their account, the pictures disappear here. Similarly, the hosting site can change their policies like photobucket did a few months ago.

If you see a really useful picture and you don't want to lose, it is best to download it onto your own computer.