Sexting is a new rage especially among teens. It carries with it many, many adverse consequences both civil and criminal. Generally, rules pertaining to invasion of privacy include such concepts as, 1) sending a nude picture over a cell phone is illegal if the sender is a minor, 2) if the owner of the cell phone receiver of the nude picture is a minor and/or 3) if the pictured nude person is a minor. Simple as that.
There are many other consequences of posting a nude picture over the internet, too. Check with a lawyer in your locale to discuss more of the details.
Even if the person is an adult, if the picture involves sexually explicit activity, the producer and everyone in the distribution chain must keep records proving the ages of the individuals. It may also violate the policies of the social networking website. A simple request is usually enough for the operators of the website to remove the picture. Many other state and federal laws apply depending on the circumstances. Other countries have laws that may apply as well.
[This communication is intended as general information and not specific legal advice, and this communication does not create an attorney-client relationship.]