Documentary film participant releases are kind of unsettling things to sign. Since it's the nature of documentary film-making to not entirely know what you are going to capture on film (reality being somewhat unpredictable, generally), the releases are very broad. You sign away your right to whatever the crew captures and agree to let them do whatever they want with it.
I've signed releases for both Caitlyn and myself twice in the last month. One was for a documentary about urban agriculture, Growing Cities. A small crew came to our P-Patch during a work party to talk with the gardeners and film us at work. Caitlyn was there, helping push the top of the wood chip pile down toward the wheelbarrows. The other was for Beyond Naked, a documentary about the naked bicyclists that precede the Fremont Solstice Parade. The crew filmed Caitlyn while she worked on a chalk drawing; they've got footage of me attempting (and probably failing) to eloquently explain why I'm ok bringing my daughter to an event where we all know that a good-sized percentage of the spectacle will be comprised of people who have nothing on underneath their body paint.
I am actively choosing to trust that these people are all who they say they are, that they are Good People. That they will use their footage as they verbally said they would. Because I don't want to be the kind of person who sees a threat to me and my child behind every rock, shrub, camera or stranger.