I can't recall exactly what the name of the website was, but I had a teacher who would require all our work be submitted via email so that she could use the site to tell how much of the paper was plagiarized and how much we had actually written. I didn't find it very effective though, as I was told I had plagiarized 35% of a paper, but I honestly didn't copy-paste anything in the paper.

This is indeed a serious problem. I once posted "Lol" in a Messenger chat room, you would not believe how many times I have been plagiarized. I see it all the time, even here on Propeller. And they are so blatant about it.