Electrical Outlets and Switches require maintenance just from years of normal use. Dust can collect in the box behind the outlet and wire connections can become loose causing an unsafe arcing condition. A common sign of this is a pop or fizzle sound when you operate a light switch or plug something into an outlet. A new light switch or outlet is an easy solution in most situations.
All electrical outlets are required by code to be of the grounding type (3-prong). This provides an equipment ground for anything that may be plugged into the outlet. It protects both the user from electrical shock and the equipment/appliance that is being used.