this turned into a major rant sorry.....
even if there are only 6 manufacturers and the genuine batteries are from the same factory, the manufacturer probably applies more quality control to the stock he sells to nikon etc.
and if he gets a dodgy batch they probably go straight out the door to the grey market anyway.
this comment tends to contradict my earlier thread about getting ripped off but i believe you have less chance of a stuff up.
I use many Lithium polymer batteries ( as compared to Lithium Ion type in cameras ) in my radio control planes, i use the cheap batteries but do have a higher failure rate. But because the brand names are usually twice the price its still a cheaper outcome.
To guard against in flight failures, i charge the batteries with special chargers (like below) which can tell me how much charge they take & deliver, cell voltages etc. so i know when they are on the way out. this technology can also be used with camera batteries but i don't bother.
Finally the chances of a battery actually doing damage by overheating/blowing up etc is more dependant on the charger and also if the battery has been dropped and internally damaged - if i dropped the camera battery i would not use it again in the camera.
i have seen fires from dodgy chargers/batteries with Li-Po's and they are nasty.
With a suitable adaptor this charger for $50 ex Hong kong can both charge and discharge Li-Ion batteries and tell you the capacity, even graphs the discharge curve on your PC.
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7386
There are exactly six (maybe five now) cell makers in the world. Li-Po, Li-Ion, NiMH, and NiCad cells are well-researched technology. It always boils down to cost-containment for the manufacturers.
--
Shooting is my thing, in ISO or .308win!