While I agree that a giant danger warning will get attention, it also implies that someone needs to be the arbiter of "danger". And given how eagerly the giant Internet co's have embraced being gatekeepers, I don't hold out a lot of hope for this approach.
Yes, and not only that, on the other end, when the danger indicators become too frequent, they end up merely being seen as noise.
( E.g., see California cancer warnings on just about everything -- makes it hard to distinguish between the <thing that will kill you now> vs the <thing that may increase your chance of a curable cancer by 1/10^6>, so it all gets ignored. )
