Twitter is the number 1 most common place to get harassed and bullied. About 43% polled that they used twitter, 28% of them admitted to getting bullied.
Ask.fm is the second most common place to get bullied online. Around 36% use ask.fm, 26% of the users get bullied.
Facebook is number 3 most common place to get cyber bullied. 75% use Facebook, 54% of them have got bullied.