I think if you go looking you'll find cases where entrapment is brought up as a defense to murder charges. The bigger issue with entrapment is that it usually requires the defendant to concede the charged crime; to say he was entrapped into ordering a murder, Ulbricht would have to surrender any defense involving him not giving that order, or believing the order was anything other than what it appeared to be.

"Do this or we will kill your family" from an undercover cop?

I think you're misunderstanding what entrapment is. What you've described is blackmail.

No, that's the example I came up with in my head too. "Entrapment" is what happens when law enforcement coerces someone to commit a crime who was not otherwise inclined to do it. The kernel of entrapment isn't that law enforcement creates an opportunity to commit a crime, but that they accompany the opportunity with some kind of push or shove.

It's both. It'd be just blackmail if I did it to you. If I were a cop, it's additionally entrapment.

What about if you were caught committing a crime and a detective told you you had to help in a sting operation if you wanted to avoid chargers. In the sing operation you are told to solicit a hit from a suspected hitman. which you do and then are promptly arrested for conspiracy to commit murder. Do you think entrapment should not be a defense in this case? I am pretty sure it's the exact kind of situation the defense is intended to be used in.