I think the issue here is you are highlighting that they are bitcoiners. This exposes random audience members to being subject threats of kidnap and extortion....why do that?
To be honest, they've gone to a Bitcoin conference and so have outed themselves already. But the bigger problem for me here would be with the organisers filming them and putting it on Youtube. Did they agree to that when they bought the ticket? It's on YT forever. With the advances in facial rec software it won't belong before we'll be able to run the vid through the software and have a name.
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