As far as I can tell, the worst thing they do is sometimes charge users to access older uploaded documents.

Money which they have zero right to collect and which breaks the implied contract they had with their previous users who uploaded those documents.

And their interface is butt-ugly with PDFs completely unreadable in their HTML version - but of course they don't let you download the PDFs because they're all behind the Scribd paywall.

Hosting documents. A pretty simple task, one would think, and yet Scribd manages to do it both scuzzily and poorly.

They have to make money somehow.

A fully-general excuse. But they are not owed a living.