Posting someone else's photograph or written work isn't the issue... it's misrepresenting the work as one's own that's shady. You're right - no need to cite. No need for many things. But if I post a bunch of wrist shots in a wrist check thread and people compliment me on my wonderful watch, and my photography skills.. and I just smile and thank them... wouldn't it be odd if it turned out it was just some pics I found on timezone?