Re: so the moral of the story
>Sounds a little paranoid to me.
Yes it does, however, what is helpful is establishing professional habits.
Whilst for some clients I do remember passwords etc I still ask the IT guy to log me in and either sit and watch whilst I perform the sysadmin action or get them to be my pair of hands; it doesn't make things quicker but it helps give the client confidence that they knew what I was doing and I wasn't 'exploring' their system.
>Secret trapdoor
As a networking expert, it is a little worrying that I have all the passwords and configuration details of their network, client isn't in a hurry to find someone for me to hand this information over to, so in some ways the secret trapdoor is knowing the IP address of the management system. Fortunately, the FinDir is happy for me to leave a brown envelope in her safe...