No sure which state you live or the state at issue, but some states such as TX, have promulgated laws that makes it a crime to impersonate someone else online. The goal is to stop cyberbullying.

Under the “online harassment” law, people who post fake profiles on social networking sites, such as Facebook or MySpace, with the intent to “harm, defraud, intimidate or threaten” other people would be charged with a felony. Commercial social networking sites were defined broadly under the statue in order to encompass many possibilities, such as sites that let users register to converse with others or construct Web profiles or pages. E-mail programs and message boards were not included in the definition.

So, based on the law, you dont need to actually defame or harass another, rather, defrauding and intimidating is enough actus raes.