It depends on the climate and the biological characteristics of the worker. Dry climates are more dangerous, because humidity increases electrical conductivity and keep objects discharged. Those people whith a limited peripheral blood irrigation (their hands are always cold) have a high resistance skin, and use to keep a lot of static charge in their bodies.

I don´t use special shoes, nor a grounded table and I have never destroyed a CMOS device by handling. I must say that I live in a rather humid country and my hands don't use to be cold.

One more advice. If you have been making photocopies, touch ground before handling electronic devices. Or even before hand-shaking anyone. Photocopiers are a strong source of static electricity.

Alfredo del Rio.