Google Earth reinstalls the software updater when it’s launched. To prevent this I created an empty file at ~/Library/Google/GoogleSoftwareUpdate, then transferred ownership to root and made it read-only for normal users:

touch ~/Library/Google/GoogleSoftwareUpdate
sudo chown root ~/Library/Google/GoogleSoftwareUpdate
sudo chmod 644 ~/Library/Google/GoogleSoftwareUpdate

Seems to work so far.

–Bud