Here's a branch of the ATO, storing your passwords in plain text:

Here's a branch of the ATO, storing your passwords in plain text:
http://alexn.id.au/2013/02/27/the-ato-stores-passwords-in-plain-text/
This is a problem because people reuse passwords - and they're quite likely to use the same password for that service and for their official ATO account.  And, more fundamentally, there are a myriad ways for someone in that chain of commercial, government and third-party entities to misuse your login and you have absolutely no way of disproving it was you.