Recently, I've become aware of a trend here to post either screencaps or complete cut & pastes of entire articles, pictures included of copyrighted material. People do so innocently enough because 'it was on Twiiter/Tumblr/my friend's Facebook page".
Now whether or not Fred Bloggs has it on their Tumblr is neither here nor there really. It doesn't matter how many other people repost it, etc etc. This forum is run by one person, and anything posted on it becomes her responsibility. And you can bet, any problems about 'ownership' of reposted articles will also be her problem.

There is a simple code to live by when posting online.
1. NEVER post an entire article unless you have express permission in writing from the original writer; regardless of whether you give a link to the source or not.
2. ALWAYS investigate the original source for yourself. Just because Sally Tumblr posts it as original work, doesn't mean it is. Select a key phrase & Google that phrase.
3. ALWAYS ask yourself "will the original owner be missing out on revenue if people look at my post instead of going to their site". Most likely YES! Sites with advertising and magazines are the most common 'source' for these articles. They rely heavily on traffic to their sites or sales of their magazines/newspapers.
4. BE DILIGENT in your postings; select a small section of the writing & post that & then post a link to the source so that people MUST go there to finish reading the article.

Remember, whilst it may be posted under your user name, ultimately the buck stops with SherlockHolmes (The Boss).
Let's not get her into hot water unnecessarily.

Thanks for your understanding in this matter.