You should activate it for your network administrator only. This means however that the plugin can be activated by site admins which you want to avoid. To do this you will need another plugin that manages these access rights. Here are a few:

• http://wordpress.org/extend/plugins/exclude-plugins/
• http://wordpress.org/extend/plugins/restrict-multisite-plugins/
• http://wordpress.org/extend/plugins/plugins-enabler/