I agree with the suspicions of some in that this is really about cost. It’s very likely they tiered this data out to Amazon Glacier. It’s cheap to put in, but costs a lot to remove.
With the traffic profile they have, I can see them thinking it’s OK to eat the cost of a few hits to that tier each month. A campaign to hoover all of the data from there would likely send their cost metrics into alarm.
What Gfycat should have done is contact these archivists and be honest with them and work to some sort of cheaper solution where they could package this data into a snowball for unpacking at Gfycat and then transfer to them.
I mean, it’s pretty easy to tell if something is a DDoS attack purely if the traffic is nothing but syn-ack packets, which this traffic isn’t. It’s totally about cost.