Here's the latest guideline published on the EB part of the BRCA site:
http://brca.org/BRCA/elecboard/news/...%20pdf%201.pdf
The rumour is that the incident at the 12th worlds was caused by a charger being on the wrong setting.
LiPos are safe unless charged incorrectly or overdischarged.
But if they are mistreated then they do not always just burst into flames immediately. I have had a couple of packs that got overdischarged (faulty lipo cutoff) and they were fine that day and the next, but two days after it had happened I checked them and they had swollen up massively.