Oh, and never ever give your social security number to a doctor's office. They don't need it. It's a trap! They want it for collections purposes.
Leave that blank on the forms, and most offices won't question it. If they do question it (I've only had this occur once), tell them that you have identity theft concerns, and don't provide your SSN unless there's a utilitarian purpose for it.
Contrary to popular belief, they do NOT need your SSN in order to bill your insurance.