Security questions

I was updating one of my many web sites and it asked me to pick a security question to answer if I forgot my user name or password. 

What was your mother’s first grade teacher’s name?
What are the last five characters in your driver’s license number? 
What street did you live on when you were 8 years old? 
What was the name of your first stuffed animal?
What was your dream job as a child?
What is the name of your grandmother's dog?

What happens if you can’t answer any of the security questions?