This story of possible organised Instagram hacking bears watching:

When she tried to log back in, she got a message that her username didn't exist. She soon realized her handle and photo had both been changed, as had the email address and phone number associated with her account. She tried to request a password reset, only to see the new email linked to her account was now a .ru email: she had been hacked.

The interesting detail is that these accounts are claimed - but not immediately used.

Could someone be harvesting "real" accounts for later use?