Facebook has been known for botching some photos and letting some look good. Even some of the super well-known professional photogs I follow on FB occasionally post a photo and complain about how soft or grainy it looks. Someone once told me to upload to FB in 2000 pixels, so I downsize my watermarked versions to that, but then again I’ve heard other sizes that are supposed to be better, so I’ve all about given up. Facebook has not perfected their photo-hosting abilities. Flickr is much better. I often direct people from my Facebook page to my Flickr stream to see higher-quality images. Facebook is a good marketing tool though.