First let me say, I cannot believe I have been monkeying around with editing for 3 years and I JUST found the COW. The amount of knowledge and inspiration here is AWESOME!!! Now, down to business.
What is the rule about blurring people's faces. If I am in a public place (a park) filiming, say a band, and I plan on selling DVDs of this event for money, do I have to blur everyone's face who isn't in the band? Or do I have to get permission from anyone who appears on the DVD?
Do a search on "reasonable expectation of privacy"
Essentially, if you're at a public event on public property, people attending likely have none. (Exceptions may apply - always consult a qualified legal professional to determine your potential liability)
But generally, at the public school little league game, feel free to pan the crowd.
If you're at a ticketed event on private property - like a concert - even if it's open to the public, it gets dicier. This is why events sometimes print a presumptive release on their tickets and sometimes post public notices that taping is going on and that if you attend, you're agreeing to waive your privacy rights for that event.
One reason you often see blurred faces in videos is that the subject of the video might be something that could cast an innocent bystander in an unfavorable light. For example, if a non-customer happens to be leaning on the wall outside an adult bookstore - or is leaving a restaurant where the crew of some CHEATERS like program is shooting on a public street, someone could argue that showing their likeness in that context implies that they're participants - so out comes the blur filter.
The bottom line is that anyone can sue anyone for anything. So learning how to protect yourself from the threat of litigation is not only smart - it's often worth spending money to do properly.
People shown at public events do not have to sign releases. Speaking roles technically do as do any likenesses seen in non-public events.
Most of the time, blurred faces, like bogus 1k tone to create cuss words, is doen for effect, not legalities. have no content.. ya gotta create some type of deal.
That said, in my 25 years of making dosumentaries, never have I chased off a person by asking them to sign something. I'd rather ask forgiveness than permission in every walk of life. Don't go taking my advice, I'm just saying this is how I do it. I don't need no stinking release forms.
Another reason for blurring is when the makers of the video want to trade exposure for money, as in product placement. If they don't want a certain logo to get free publicity, they blur it out. But don't turn this around to automatically assume only paying advertisers are allowed to be seen on screen and all else MUST be blurred.