I have never blown a lighter up, but I found the following:

Snopes.com has an article that debunked a spark from welding causing one to blow up, but then goes on to say that they do indeed blow up from heat, and have blown up in peoples pockets.

http://www.snopes.com/horrors/techno/lighters.asp

MythBusters did a segment where they couldn't make one explode.

Canada customs agents confiscate certain lighters they say explode:

http://www.cbc.ca/news/story/2000/11/06/lighters001106.html

Adults may carry lighters, not youth. Matches and hotsparks are OK.

BSA policy is to make sure the boys have safety training before carrying knives and matches, therefore the chip & chit requirement. We usually try to get all the new scouts through the training the first campout. After that, any unsafe act gets a corner off the card. Not carrying the card when carrying the material will get a corner off the card (when it can next be found). When all four corners are missing, back to training to earn a new card.
_________________________
The Seeker