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.
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.
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.