At last weekends ROAR (US governing body) meeting it seems a rule was passed that outlawed the use of LiPo batteries in all R/C cars that run at ROAR sanctioned events. Although not stated, the reason was probably down to the safety issues with these batteries having been known to explode if not charged and handled properly. This is unfortunate as the benefits of LiPo are clear (weight, size, longer runtime) but i think this move was more a case of covering ROAR’s ass in the event of an injury brought on by an exploding LiPo. The move however seems a bit extreme as danger is present in all forms of RC racing, particularly burns and cuts and the mis-use or bad treatment of any power sources will always result in an injury.
The ruling however does not just affect Electric class racers but also gas racers who have installed LiPo cells to power their receiver. The judgment makes no differentiation between uses of the cells, but instead just bans their usage in all classes outright.
From the minutes of the meeting:
A proposal to outlaw Lithium Polymer batteries in all r/c vehicles was discussed. This item was adopted.
You can read the full minutes of the meeting here (PDF).