應該, 但是應該談"total compensation"

Telling your current income does not hurt your position. Telling a lie can potentially hurt you badly. Telling your income can save you time, as others suggested. What important is to consider/negotiate the total compensation, and know what you want. Especially when you have a reasonable position, you just tell the other party you are worth of that much. Total compensation and benefits are what count. Think about 1 more week vacation yearly - not only it makes your hourly salary high, it also set up a platform for your future negotiations.