Where is the line between teasing and bullying?

It is my feeling that if someone feels like they are being bullied, and it is not in good fun, then it is bullying. However, if the person being bullied does not show or say they are being bullied, how can the other person know if they are engaging in bullying behavior?

I know my parents would tease me about some things, believing it was all in good fun. I never showed it, but inside, these comments were very hurtful. I’m sure this often happens between parents and children and the children don’t feel they can say anything.

What do you think? Have you had any experiences, either taking teasing from friends or parents that bothered you more that you were willing to let on or giving it but not being sure if you were crossing a line?