It's not unheard of in the sense of never having happened, but it is a clear breach of ethics for a security researcher. (The term for not doing what these guys did is "responsible disclosure").
I'm not saying the non-security researcher users on HN have an opinion representative of the public as a whole, but this comment and a previous question asking another user what security research they've published may point to such an ethics disconnect between security researchers and the broader populace -- or simply a disregard for the concerns of the broader populace. I think it would be beneficial for security researchers (or any professional group) to listen to ethics concerns of the broader group they're a part of.
On another note, I would also assert that abusive actions by vendors do not excuse abusive actions by researchers (and vice-versa).