I've never seen anything on this but if you know about this disregard
I have two similar sites pulling the same feeds, and are roughly the same domains (one is pluralized form of the other) I noticed that one has weird stuff indexed (ie feedlinks, wp login page etc.) and seems to be neglected by google while the other one seems to be indexing fine.
I had a hunch because of what was being indexed on the one site might have something to do with theme I was using.
If you use firefox and the webdev plugin you can disable styles and see the page as a spider would.
Sure enough when I compared the two themes without css styling, one was displaying all the menu stuff up top, while the other one had all the menu stuff at the bottom.
I am going through a lot of the themes I usually use to see if there are any more that behave like this so I can switch them to the theme that displays the content up top rather than menu stuff.
Theme designers here, you should check out your templates to see how the content is really displaying.