If you have tried some of Google's software, Chrome for example, chances are that you have Google's updater on your system now. You might not even know this because the notices during the install process are easy to overlook, and the updater gets installed in places that you normally don't check.
Whether you want this background process running on your system is a different story, but at a minimum it should disappear when you uninstall the last app from Google; and this is what should happen in theory, but it's not what I've seen in practice.
So, here are the steps to manually uninstall the Google updater.
1) Check the "LaunchAgents" folders in the Library and ~/Library folders for a Google "keystone agent" and remove that.
2) Make sure that the system's launchd doesn't waste time looking for the (now deleted) keystone agent:
launchctl remove com.google.keystone.user.agent
3) Delete the actual updater from either Library/Google or ~/Library/Google.
This should be it. You might have to tweak step 2 depending on what kind of admin rights you had when you installed the Google software as the agent might have been installed on a system rather than a user level.
As a side note: I find it interesting that the installer seems to prefer to write to the system-wide library folder, and only if it doesn't have permission falls back on the user-specific folder. It doesn't ask you, like the system's font, widget, or pref pane installers, where you want it. Surely, only a suspicious mind would assume that this is to avoid making it obvious to the user that some form of background software is installed in the first place...