Figure its worth bumping this since with the question of hard translated copies came up in topic #10710, it seems like anything done here will also help greatly with that whole issue
I think the main things are to discourage uploading samples, since they really don't offer anything. They're a few pages, tend to be smaller, and encourage the posting of the complete doujins, even if the originals aren't there.
I'm fine with pixiv, or other web-doujin, but I think that allowing printed doujin causes a series of issues.
There is the issue of post quality, not all scans are equal and while danbooru's note system helps translators greatly, by allowing easily created and edited translations, there is a very finite amount of translators. Dumping 20-30 page doujin creates an issue of just having a large amount of untranslated, generally undertagged posts.
I also think that its bit of a gray area for artists. Some artists are already unsure of danbooru already, and encouraging the posting of raw scans is pretty much endorsing piracy. I'm not interested for reasons of legality, but I think its just a bit unfair and puts us in a worse light.
Part of will help will be creating a separate tag for doujin, but I hope there can be way to set it up so that doujin that are freely available can be separated from those that are scanned in a relatively painless way.
And looking at it, we have three janitors who are pretty loose with approvals. Myself, not_one_of_us, and zigzag. Not one of us in particular has a long history of questionable uploads, but I haven't got any negative feedback and nor has zigzag.
Before things escalate, I think its worth just formalizing what should be done and making sure everyone knows whats happening.