"So, they just found out that eating too much chocolate can cause kidney disease. Yeah, they're saying that dark chocolate is actually really bad for you, contrary popular belief. Yeah, isn't that crazy? First they say it's good for you, then they say it's bad."
You can infer that "they" refers to some type of medical authority or research establishment, but technically, "they" COULD just refer to two crazy guys at the bar who told me this story. Nonetheless, it seems to give the illusion of authority. It's also a really good way for a person to pit him/herself against an imaginary opponent and appear rebellious:
"They say that spending too much time working is bad. But you know what? I love my job. And I love working."
Does this happen in any other languages? Can "they" be used for the same purpose in any other languages (i.e., authority, hiding the source, etc?)