When a human's body capacitance is charged to a high voltage by friction or other means, it can produce undesirable effects when abruptly discharged as a spark.
The influence of body capacitance on a tuned circuit may also change its resonant frequency, which would affect the performance of radio receivers.
Notably, a combination of footwear with some sole materials, low humidity, and a dry carpet can cause footsteps to charge a person's body capacitance to as much as a few tens of kilovolts with respect to the earth.
Although the occasional static shock can be startling and even unpleasant, the amount of stored energy is relatively low, and won't harm a healthy person.
The spark may damage sensitive materials or electronic devices and in exceptional cases may ignite flammable gas or vapor resulting in a fire.