Although it is possible for LiPos to explode.. at our track folks have been using them for racing for over a year now... not one has blown up.. we have had many.. many NiMh pop...
I've seen some of these videos where they use a drill to show you what can happen.... I don't know about you guys.. but in the nearly 2 decades I've been racing, I have never had a crash as bad as a drill going through my batteries! lol
They seem to be pretty safe... It is probably smart to at least use the hard cased type..
Jerome