I would never share my current salary with anyone that can use it against me in negotiation.

If a recruiter asks, I tell them I'm not comfortable sharing it. If they press, I tell them that I only discuss numbers once the company and I both agree there is a mutual fit.

No one has ever told me they will not proceed without my current salary, but if it ever came to that I would thank them for their time and hang up.

Isn't there a lot of potential to waste time that way though? If they're expecting to pay 80K and you're expecting 140K?

Then they should say what they are offering. Don't forget: they could give a number, too.

This is a good policy. I know it's an unwritten rule that you don't tell someone your current salary when you're interviewing for a job but I like the way you put it. My professor last year said if there is a required field on a form you need to fill out then just put $1 for your salary. I've always appreciated that and followed it.