From my own personal experience I have found that GoToMeeting has solid privacy features.
When you create the meeting, in addition to receiving a personal meeting ID code, you are given the option to create a password to enter the room to create an extra layer of security. Organizers of meetings are able to dismiss attendees of the meeting very easily, by clicking on the attendee in the control panel and removing them, as well as cancelling the meeting at any time. As an organizer, you are also given the ability to disable chat for one or more attendees at any time.
If you are trying to share screens, the organizer can select one attendee who is able to present to the entire meeting. Another plus of GoToMeeting, is that you have the ability to enable, disable or pause sharing of multiple screens or individual applications while searching for files, so that you aren't sharing confidential and personal data.
Overall, GoToMeeting has a solid understanding and utilization of privacy features and administrative controls, so that you feel that you are in a secure environment.
You can learn more about GoToMeeting's privacy features here.
This user rated GoToMeeting's administrative controls: 4.0