I don't think theft is a common occurrence, and if it does happen, I know Wattpad takes it very, very seriously. One of my friends posts her works in progress here on a regular basis...I'll ask her about it and get back to you :)
@ShantiKrishnamurty I really want to post the start of my new story...but I'm afraid...how safe is it??? Will someone steal my story? Am I being paranoid? :)