A topic that pops up here regularly enough but here's one I hadn't seen before.
I'm just back from the Isle of Wight festival (as a punter, not a tog). One of the stands was run by Ray-Ban sunglasses and at the entrance to their stand they had a big notice which effectively said "By entering this stand you agree to be filmed/photographed and those images can and will be used commercially by Ray-Ban". (Not an exact quote but near as be damned). So just as a browsing member of the public I was either filmed or photographed secretly (I didn't see any cameras) and I gave them the right to use my image in a commercial fashion!