No one likes having things weigh on them. Especially your electrical outlets. When a plug enters an electrical outlet the plug is held in place be a spring loaded clamps that pinches the connections on the plug. Springs wear out and become less effective at holding the plug in place over time. Heavy items like a plug in air freshener will cause the spring to wear out much quicker than they would under normal use. Have an outlet that plugs almost seam to fall out of? It is highly recommended that plug not be used until it can be replaced. Loose electrical connection cause the electricity to “arch” inside the plug and arching causes heat. Although some electrical outlets can last much longer, they should be replace every 15-25 under normal use.