What about the accusation that you stop the negotiation when a candidate refuses to disclose their previous salary?
Our culture is really built on two-way trust: since we're distributed and seldom see each other you don't know how someone is going about their work, and most of our HR policies come down to the honor system. The company places an incredibly amount of trust in employees, and vice versa people place a great amount of trust in the company, including that we'll do our best to treat them fairly. It's a responsibility the folks on the operations side of Automattic, including myself, take very seriously.
If knowledge of a candidate's previous salary doesn't influence your offer, why do you ask for it and what do you do with it?