I always trouble myself in my postings to paraphrase or otherwise alter any information that I obtain from published works (and I was stopped from linking to records on CANMORE). Surely it is still breach of copyright to publish chunks from books even if you give the name of the presumed copyright holder and append a full bibliography ? Many on the web are rather more than extracts of material reproduced for educational purposes. But especially I am troubled by those who post to the web copyright graphics eg. plans and diagrams. Very occasionally I shall use copyright graphics in making works of my own, but my transmogrifications themselves result in essentially new works.
On a related matter the problem with linking to RSS feeds comes when the relevant website quotes the material itself on their pages.