Saw this on UKClimbing.
Although it applies to via ferrata safety equipment, it looks like the problem would also apply to elasticised ice tool tethers, although compared to ferrata lanyards, which are the belay if you fall, it's rarer or unlikely that those would be in the sole position of stopping a fatal fall (unless you are in the position of using your tethers as body belays while soloing, for instance)
http://www.ukclimbing.com/news/item.php?id=67412