Follow-Up:
Yes, I've had an earth curb pull the rubber coupler right off the sewer tank, generating a slow leak that resulted in a free dump all the way home. Other than going over curbs or other true obstacles, I haven't had a problem. You just have to keep it in mind when driving, and you'll quickly recognize what you can and can't drive through/over.
Here is a link that might be useful: www.MotorHomepage.com