I have TD portable to sync files on a USB stick.
I did not find an option to logoff or to have TD ask me for my password on every new run.
It is a security issue if the USB is able to automatically login to TD just by having anyone (not me) clicking on the TD.exe without any verification.
On the PC, as it runs under a protected account, this is not such a problem, but still it should have provided an option.
thanks
Mike.