A 5kv static charge generated while walking across a carpet has little current capability, but at least a couple of electrons can blow thru the very thin material surface in a MOSFET, possibly causing a permanent fault in the surface material. Floating inputs on semiconductors can cause unexpected behavior. I made a video switcher using a 4017B chip, and when the clock wire was left to float, it would start switching on its own when my cat got within ~1" of the wire.