I don't agree nor disagree with you. :-) A great site is only great with good content - be it either text or images. There are plenty of sites to be found on there where imagery is sparse but the typography is beautiful.
No. I'm just going on the assumption that everyone would like to see traffic to their site, and I make it clear in the footer that all screenshots are the copyright of their owners.
In its history (since 2009) I've had one take down request, from a photographer who was tired of having his work ripped off so wanted to keep a low profile.
Their argument is that commentary on the original Digg was essentially the first of its kind, whereas commentary happens "everywhere" and they need to spend time aggregating commentary too. Not sure how they can do this effectively, but will appear over the next few releases.