TitanusOptronix said:
I just wanna ask, how many people actually ask an artist for permission before uploading their stuff? Are there some cases where it is acceptable not to? Do some artists not need permission?

The official position is that you should always ask the artist for permission before uploading their work to the site.

Cinder said:
The official position is that you should always ask the artist for permission before uploading their work to the site.

So the janitors can assume that they got permission before posting unless shown otherwise