I agree that an object can orbit at less than 300km, but I generally tend to think of "orbit" a being located at one of the Lagrange points.
Most of the more modern (post 2000) communications networks (just to name 1 type of network), when their satellites run low on propellant and therefore lose maneuvering ability, use their remaining propellant to put the satellite in a 'safe' parking orbit.
Unfortunately the moon tends to impact a portion of these 'safe' orbits every year and we get "rogue satellites" (search for that term and you will find many references) that tend to have elongated orbits as their altitudes decay. These elongated of orbits (like ellipses) tend to cause the rogue satellites to increase their velocity (on the minor axis of the ellipse, they go slower on the major axis) and, while this usually contributes to their faster burn up, they can become very unpredictable and therefore very dangerous depending what is actually reentering.
Edited by LaurieAG, 01 April 2019 - 11:54 PM.