I have seen a lot of blogs on tumblr and around the net that use adult pictures from all over the place and they don't seem to have any problems. They provide info at the bottom to request takedowns. I recently started a blog and I find unwatermarked pictures from places like adult tumblrs, blogs, chans etc and post them on my blog. Most of them are amateur self-shot photos however some are just unwatermarked but seem professional. I also considered putting a watermark of my own domain on the pictures as they're uploaded to my blog in the hopes this will help with promotion. What are legalities I should be concerned with as far as using the images?