Legally, how would this differ from a monkey stepping on a remote trigger, or stepping in front of a motion detector to trigger a camera to take a picture? Are all of the pictures on Snapshot Serengeti (http://www.snapshotserengeti.org/) copyrighted by the animals in them?
Of course only humans can hold copyright. But an issue here is, the photographer never intended to take the picture (in this way); it was an accident. So its debatable.
It's not an accident - the photographer recognized the opportunity, and allowed the animals to continue. He put himself there to be part of the animal's scene. He was there to photograph the animals, and that's what happened.
Ultimately, every photograph is an accident; nothing bad happens in between the photographer's recognition of the correct moment, and the exposure of the medium. That time is non-zero, and bad things can happen in between those times, and when they don't you get the photo you want.
And how many photographers hold down the shutter, while they reel off a dozen pictures, hoping that one of those photos is a good one? Were those photos "accidents" and therefore not copyrightable? I don't think the courts would agree.
I'm actually interested in seeing this go to a decision in the courts. There's clearly a division of opinion in the discussion here, and it would make for an interesting case and precedent.
Probably not a lot of 'allowing' going on - don't want to get between a Macaque and its toy.
Anyway the idea is, the requirement for copyright is "developed independently by the author" and "some creativity involved". It was not 'by the author. And is it creativity if its an incident totally out of the control of the author? Debatable.
So if my phone takes a picture when taking it out of my pocket, is it immediately public domain? I would guess that it being accidental wouldn't play much into it.