Introverts can sometimes be picked on because they tend to be quieter. They can be misunderstood as being anti-social. Bullying can be trickier to manage as an introvert because you might be less likely to speak up for yourself or less comfortable with asking anyone for help.
Source: What does it mean to be an introvert? @ ReachOut.com: Get through tough times
image: Lonely by Lilong Dolrani under Creative Commons license