As others have mentioned, this was probably due to inactivity. I stopped using Instagram years ago, but still had 'instagram.com/derek', and just checked to se

As others have mentioned, this was probably due to inactivity. I stopped using Instagram years ago, but still had 'instagram.com/derek', and just checked to see if that was still my username. Nope, it is now 'derek______________', just like '_____kathleen'. The fact that a FB employee now owns the 'kathleen' user means they probably have an internal reservation system for expired accounts, which is a nice perk.