the thing I would be most worried about would be a freaked out person, most likely in shock, start grabbing at the skids. Even if your intent is just to drop a flotation device, thats certainly not the thing going through their mind. It would be nearly impossible to communicate to the person, not that they would listen anyway. All they'd need to do is get a good grip on a skid, and I wouldn't be at all surprised if they brought you down.
I remember reading an accident report where a pilot was picking up passengers on a boat, and an impatient passenger jumped on the skid and put the helicopter out of cg limits. There was absolutely nothing the pilot could do. the helicopter drifted right, into the ship and killing two other crewmembers on the deck, not to mention balling up the chopper.
I've thought about a similar land-based scenario before. Your on a night flight, and you notice a flashing light. After looking closer (and thanks to your handy dandy boy scout training) you realize that its an SOS signal. It could be someone in serious trouble who needs help. It could also be some jerk who likes to play tricks on passing aircraft.
I think the best course of action would be to call the forest service or whoever else is better equipped and trained to help. stay on scene to help the SAR guys locate the wreck, but dont forget about how much fuel you have. If you have a life raft on hand, drop it, but keep your distance. Theres no need to turn 1 accident into 2.