Yeah, opt-in is an attractive nuisance when deciding things like this. It's a good way to argue that something should be allowed because you did your due dilige

Yeah, opt-in is an attractive nuisance when deciding things like this. It's a good way to argue that something should be allowed because you did your due diligence and warned the user, but in practice it provides very poor security (for the reason you give). At the end of the day, no amount of purism and theory can ever outweigh the actual effects.