Alastair makes a good point.
I often written articles for my Blog which have raised a huge amount of interest around the web. These articles are routinely linked to from forums and other blogs (which I have absolutely no problem with, and that is quite lawful) but in other cases a blog or website about a similar subject will repost my article and pictures in its entirety on their own blog. The fact I may have received attribution is irrelevant in my view, what they have done is use my work to create fresh content for their own website, generating additional traffic to their site where the viewer can stay and read the full article without having to go to my blog at all. I am happy to be a guest blogger when asked, but I do see a lot of my work republished in full, not in the UK but usually in other European countries. Normally this is quite easy to deal with, and I'm happy to come to a more equitable arrangement with the site concerned, but full-on embedding of wording and images should not happen in the first instance without permission from the originator. The argument that an article/picture is already "publicly available" elsewhere could understandably open the floodgates for plagiarism and copyright infringement. I believe there is leeway when it comes to educational use, but as I understand it that would relate to use within actual educational institutions rather than anyone simply deciding to use someone else's work in order to provide engaging content to their own readers, and to boost their own presence.