There are a lot of issues with Lithium cells that are not adequately understood and/or suitable for use by the uninitiated. The Boeing fires are possibly caused by Dendrites. Who even knows what they are and how to manage them?? http://online.wsj.com/article/SB10001424127887324880504578298673566960476.html?mod=djemalertNEWS

Convenional batteries won't normally explode or burn unless grossly mismanaged. Even then, if there is adequate ventilation, you'll just ruin the battery, not have a possibly catastrophic fire and/or explosion.