I have had a request for my complete salary history, and this is prior to a phone interview with someone with a technical background. I do not think that my worth should be gauged for a new position by what I am making now. And just as a matter of course, I recommend not divulging it for the very reasons you mentioned. Once your past salary is on the table, your negotiating edge goes out the window. The entire purpose of an interview is to allow both you and the employer to assess one another's value in terms that are meaningful to each of you, not to anyone else.
Value is relative, and it's worth figuring out.
To do less is to shortchange yourself and the party you are dealing with. But that doesn't make their request right or fair. Please see my recent column about keeping your salary history confidential . I think you'll find it useful. I really enjoyed them.