"This is an important message from Amazon.ca.
At Amazon we take your security and privacy very seriously. As part of our routine monitoring, we discovered a list of email address and password sets posted online. While the list was not Amazon-related, we know that many customers reuse their passwords on several websites. We believe your email address and password set was on that list."
Should you wish to prevent systemd being installed when updating from Debian Wheezy to Jessie create a file like
Package: systemd-sysv Pin: release o=Debian Pin-Priority: -1
and ensure you uninstall the Gnome desktop and choose another as that has a "requires" dependency on systemd. Do this before changing the wheezy entries in your
/etc/apt/sources.list or the more modern
/etc/apt/sources.list.d/*.list components form to the jessie ones.