Everybody who has children knows about the constant feeling that you need to be monitoring their safety as they roam around the house playing and discovering their surroundings. Every table corner, flight of stairs, or small object is a potential hazard to a toddler. Home electrical outlets have always been on that list of things we need worry about. Anything that can be inserted into the outlets could potentially conduct electricity to hurt the child.
The National Electric Code (NEC) is a code set up by the United States published by the National Fire Protection Agency added tamper resistant outlets to the specification required for new or renovated dwellings. The newly mandated outlets have two spring-loaded (one on each hole in the plug outlet) that cover the contacts within the outlet. When something is plugged in the outlet, both springs are released and the contacts are exposed to complete the electrical circuit. Both springs have to be activated simultaneously to expose the electrical current so if a child were to insert something in one of the holes on the plug, nothing would happen and the child's safety would be insured.
These codes apply to all homes, regardless of whether the owners have children or not. Many children are injured in electrical accidents every years at a friend or relative's house. The new safety features on tamper resistant outlets only add about 50 cents to the price of a new outlet so the cost is negligible compared to the increased level of safety.
Current homeowners must choose if they want to retrofit outlets in their existing house. If you have children, it would be considered a must to put in tamper resistant outlets. Most people could do it themselves but a professional electrician could always be hired to make sure the job is done right. If you have just moved into a house, you can tell if your outlets are tamper resistant by a "TM" that must be visible on the outside of an installed outlet.
This national code is quickly spreading to all local and state municipalities, check local codes to see if your area has officially adopted the regulations.