In my experience with GoToMeeting, I have not seen any issues with security.
First off, GoToMeeting uses strict encryption protocols to ensure that anything that is shared during your meeting remains confidential and secure. Each individual meeting is kept secure, as only those that have access to the session ID can login to the meeting. Another added layer of security is to add a password to your meeting. That password is never transmitted, so you can be assured that it is secure and can't be found by anyone you don't want it to.
GoToMeeting provides true end-to-end data security measures, so that all connections are end-to-end encrypted, so you can be sure that your meeting will remain confidential.
GoToMeeting does offer SSL and TLS protocols to add an extra layer of security. In addition to SSL, GoToMeeting uses VeriSign/Thawte public key certificates that prevent would be hackers to impersonate as infrastructure servers to steal your data.
For more information on GoToMeeting's security, take a look at their white paper.
This user rated GoToMeeting's security features: 5.0