I find recruiters hurt this more than help it too. If you tell them your last salary, they'll just try to get enough % more to make it worth the transition.
That's what I don't tell anyone what my previous salary was. I am looking for X dollars per hour, do you have anything for me in that range? Yes or no...
That's it. I'll generally let them know it is open to negotiation as well.
After all, some companies suddenly become "flexible" once they find a candidate who really blows them away. Their alleged "top range" becomes malleable. So their range can be imaginary as well. In the information war that both sides are waging, similar tactics can be used.
That's it. I'll generally let them know it is open to negotiation as well.