Burke-Gilman bike ‘carcasses’ a mystery

Charlotte has noticed quite a few stripped bike frames along the Burke-Gilman Trail recently. She writes:

Anyone know what’s up with the ever-increasing number of bike carcasses on the new bit of the Burke-Gilman behind Paseo at Shilshole? A week ago there was one stripped-out frame leaning against the fence by the railroad tracks. Then it was joined by another carcass near the traffic lights. And the other night my husband nearly hit yet another one, this time in the middle of the same section of path (no lights on that part of the trail – night users beware of obstacles!). As of yesterday all three skeletons were still on the trail. Anyone got any theories?