I used to fly electric model airplanes. Here are a few things to consider:
First, I've seen numerous comments about misuse, dropping, etc. I never had a battery go into runaway from dropping them. The one thing mechanically you do have to watch for is punctures. I know of at least one case of a crashed model airplane catching fire. It's unknown if it was from a puncture, shock, deformation, etc.
Second, over-charging can definately cause smoke and fire. A lot of fire. Think road flare type flames. I've seen it first hand. People have burned houses down by over-charging LiPos. Some say newer batteries are a bit safer. I'm not convinced.
LiPos are rated by storage capacity and discharge rate (the C value). To get max discharge in amps, you multiply the C value by the storage capacity (in amps). Some also give the charge capacity (also a C value). I always charged my batteries at one C. The "S" on LiPos means number of 4.2 volt cells in series. Smart chargers are a must.
I always kept my LiPos in an ammo can. I always charged them on a non-flammable surface with at least 2 feet of clearance. The one battery I saw go up in flames shot a flame about a foot long out both ends. There was nothing left but ashes, a scrap of wire, and the connector.
The accepted method of rendering a suspected batter safe is to puncture it and immerse it in salt watter.
Low voltage is a battery killer. Go below the recommended minimum and the battery is pretty much done. Sometimes you can cycle them and bring them back. Cycling means charging and discharging a number of times.
Make no mistake, these thing can be dangerous if misused. But used safely, they work great. If you build with them, just be careful and don't short them in the process. If you do, toss the battery (after the salt water dunk).
I used Turnigy and Zippy batteries from HobbyKing -
http://www.hobbyking.com/hobbyking/store/__86__85__Batteries_Accessories-Li_Poly_All_brands_.html
