This just hit the news yesterday. The Lovett School is a private day school in Atlanta. These were 8th graders. And though I certainly don't condone this behavior, the kids who passed it along may face charges as well of misdemeanor child pornography. 'Sexting' Rocks School; Student Withdraws - News Story - WSB Atlanta
I'm already talking about it with my 5th grader. I can easily imagine kids receiving something like this and not thinking twice about passing it on, having no idea how serious the consequences. I plan to mention it to my d at BS as well the next time I speak with her.
The same caution goes for anything in email form that can be misconstrued as threatening/bullying. The written word alone can be easily misinterpreted or misconstrued. I know of an email incident where references to a school project on government regime change got misconstrued as terroristic threats. And though there was no ill intent, several of these otherwise very upstanding kids were named in a police report.