First kill any zeitgeist process that's running (ps -ef | grep zeitg should display any instances).
Then, from SilverWav:
# Delete previous logging. rm ~/.local/share/zeitgeist/activity.sqlite # Render Zeitgeist illiterate - cannot read or write chmod -rw ~/.local/share/zeitgeist/activity.sqlite*
SilverWav also recommends running zeitgeist-daemon --replace, but I do not, since I just killed the damned thing. Note that SilverWav is talking about neutering zeitgeist on Ubuntu 11.10, so this hasn't infected Mint alone. One thing I did differently than SilverWav was to just delete the contents of activity.sqlite rather than deleting the file itself.
The second order of business is to take zeitgeist out of the startup list. The startup seems messed up in Lint 12, since the startup list is pretty much empty (this is probably so neophytes won't disable things they need). Look at "Startup Applications" on the "Other" menu, which is a weird place to put it IMHO. To make the automatically started applications visible on the startup list, follow this suggestion from the Mint 12 Tips & Tricks Guide at linuxmint.com:
sudo sed -i 's/NoDisplay=true/NoDisplay=false/g' /etc/xdg/autostart/*.desktop
It might be worth having a look in that directory periodically for new applications or updates that surreptitiously add themselves to startup. Now the startup list should be fully-populated and you can get an idea of exactly how bloated Linux Mint 12 is. On my startup list, the last application was Zeitgeist Datahub. Uncheck the box next to it.