You can uninstall or removes an installed geoclue-plazes package itself from Ubuntu 12.04 LTS (Precise Pangolin) through the terminal,
$ sudo apt-get remove geoclue-plazes
If you would like to remove geoclue-plazes and it's dependent packages which are no longer needed from Ubuntu,
$ sudo apt-get remove --auto-remove geoclue-plazes
If you use with purge options to geoclue-plazes package all the configuration and dependent packages will be removed.
$ sudo apt-get purge geoclue-plazes
If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.
$ sudo apt-get purge --auto-remove geoclue-plazes