A QUESTION: what is the private, cherished, legal act that is illegal to photograph or videotape, even with the consent of the participant?
No, the photograph doesn't have to cross state lines. The answer, at least in North Carolina since 2007, and presumably in other localities, is voting. Specifically, "No person shall photograph, videotape, or otherwise record the image of a voted official ballot for any purpose not otherwise permitted under law."
The reason is not, as you might suspect, voting voyeurism. Rather, the fear is that by allowing people to record their votes for posterity the state could be encouraging the sale of votes, as in, "Here's a picture of my completed ballot, now where's my five bucks?"
Despite new laws like North Carolina's, the 2008 election will surely be the most recorded in history. The reason is simple: most voters these days carry the necessary equipment, and the Internet lets these images be shared instantly.