the footage becomes theirs and they are free to use it as they wish no? Plus they've tempted you with a phone that if you want you're going to have to fork out a lot of money for. Instead of (or as well as) commercials costing hundreds of thousands, they just spend a little on some phones and postage and get people to do the hard work.
I'm not at all hating on them, it's a clever way of getting their name out there, but personally I would be wanting more (like a free phone if they use your footage or something). But I guess you're right in that not everyone has a camera, so it is a free way to borrow one for a while.