There is information in the FAQ section
of the Scribd site that addresses copyright isues; the onus seems to be on users to not upload iffy stuff in the first place, and to report iffy stuff that does appear. One section says:
"What types of items are not allowed on Scribd?
You may not upload content for which you do not have the necessary legal permission. Always be aware of a document's copyright status. You may be held responsible for copyright violations.
Scribd is for the publication of personal documents only. You may not use Scribd for HTML advertising and search engine optimization.
You may not upload any content considered illegal in the United States.
Scribd does not permit racist or hateful content.
If you see content that violates these terms, please use Scribd's document flagging system and the document will be reviewed. Be sure to read our Terms of Service for more information."