Continuing from the suggestion in forum #46405 that some of the removal requests we get are from artists who don't understand exactly how Danbooru works, I've written a little something in English to describe the pros of leaving your work on Danbooru:
Danbooru's goal is to provide its users with a database of high quality artwork, with a special focus on Japanese artists that might not be seen by international visitors otherwise. To do this, pictures from sources such as Pixiv are often copied without the artist's explicit permission. However, Danbooru users do not claim any artwork as their own, and, whenever possible, creative works are attributed to their rightful artists.
Whenever a picture is uploaded to Danbooru from an artist's Pixiv account or blog, several tags are attached describing that picture's content. (A picture's tags are visible to the left of the picture, under the header 'Tags'.) One of these tags, colored red, indicates the artist of that picture. By clicking the '?' next to that tag, users can see the artist's name in both romaji and Japanese script, and can follow links back to the artist's Pixiv account or blog. In this way, users without knowledge of the Japanese language can become fans of Japanese artists.
Danbooru respects artists' requests for removal of their artwork. If you believe a post infringes on your copyright and wish to have it removed, please send an e-mail to the webmaster (firstname.lastname@example.org) with the URL of the infringing post and proof that you own the copyright. However, we hope that you will consider allowing your work to remain on Danbooru for the sake of your non-Japanese fans.
This is a first draft, so please feel free to make and suggestions for changes or additions. Once we've settled on something, perhaps one of our users who speaks Japanese natively could translate it, and we could have albert put it somewhere visible (my suggestion would be between "Recent approvals" and "Help" on the "Posts" subheader), with a Japanese header so that Japanese artists' eyes are drawn to it.
Updated by juunigatsu no usagi