Obviously both of them already do some content filtering for illegal content etc. but where do we draw the line? Personally I think it's unfair to be blaming them, considering they never claimed to filter this type of content. Also, if it is decided that they should be responsible, how do you determine what is and isn't fake? Seems like a dangerous thing to be in charge of.
edit: since it took me so long to finish typing this, everyone is now asking similar questions. whatever