The two main prongs of interest are attached to their respective contact strips using a single square stake, punched down the middle to expand and lock it in place. While this does a great job of ensuring that the slugs don't get left behind if the adapter is ripped from the wall outlet, a single point only eliminates three out of six degrees of freedom. It is locked in for the x, y, and z axes, but given any slack or force, it will still pitch, yaw, and roll by some amount. Movement from normal use will inevitably wear it down and work it loose.
A loose connection becomes a nuisance at best when it causes your devices to randomly lose power. However, it's a fire hazard at worst under non-trivial load.