What are these teardrop-shaped loops in power lines for?

I always assumed it was a way to store slack in a cable like coax or fiber that can't be bent sharply without damaging it. I followed the "Snowshoe" link Michael posted, and it appears that I'm right.

SmackmYackm: Cable Guy here. It's intended purpose is to store spare fiber, and we actually do call them snow shoes. There are dozens of reasons you would want spare fiber in a given location. Usually there will be a splice enclosure nearby.

SmellyFinger: I actually work for the company that makes [snowshoes] ... they are used to manage slack storage in an aerial cable network (comm and not power, and specifically for fiber cables). They keep the cable from bending too tightly when stored on a span as seen in your picture. They are not made to slide, even if a tree falls on the line (they might slide, but they aren't designed to). They come in various sizes and can be painted aluminum or molded plastic like this one is. Sold as a pair.

brock_lee: It's a loop. To run a wire from pole 1 to pole 2, they run it from pole 1, around a loop, back to a second loop, and then to pole 2. This helps prevent a disruption of service should a pole fall down or something fall on the wires. The loops allow the wire to uncoil or "stretch" rather than break.