I wish it were easier to give credit to creators rather than curators online (or worse, plagiarisers). The fact is that it's way easier to just credit the person who shows us something cool than to go looking to see if it is being properly attributed.
Perhaps we should be in the habit of watermarking all photos, videos and audio with creator info so that it's easily discovered no matter where it goes. If it's important information about a file, it needs to be inside the file. That doesn't mean plagiarisers won't be able to re-mark a file to claim it as their own, or that someone can't steal the idea behind a piece and produce something similar on their own. It would just make it easier, when someone shares a video or picture online honestly, to track down and inform the creator that their work is being shared.
Mokalus of Borg
PS - Of course a lot of sharing is just linking these days.
PPS - However, linked or copied, marked by the maker is best.