From the designer, Tom Scott:
"It seems a bit strange to me that the media carefully warn about and label any content that involves sex, violence or strong language — but there's no similar labelling system for, say, sloppy journalism and other questionable content.
I figured it was time to fix that, so I made some stickers. I've been putting them on copies of the free papers that I find on the London Underground. You might want to as well."
You can download the template and read more about it here.