It's purely a misconception in the same way that 30% motor oil is pure orange juice -- which is to say, it's not a misconception, by my reading. I wonder what my IP laywer would say about it, will post if I decide to ask.
Unless I am looking at the wrong comment, @pluma's explanation is just that it's not a problem as long as you don't sue Facebook. But this is equivalent to saying that as long as you give up your only recourse in the event FB violates your IP, you'll be fine. To me it seems like a mentality that makes sense primarily if a person doesn't ever expect to do anything worth patenting, or doesn't ever plan on patenting for some other reason. Don't sell yourself short.
