Before you buy that eBay camera battery...
 

The Camera & Imaging Products Association warns of counterfeit battery packs that could damage your camera or cause you injury.

It has been confirmed that recently counterfeit lithium-ion battery packs for digital cameras made to look like camera manufacture's genuine products have been circulating. Incidents where battery packs have exploded have also been reported, and these incidents are thought to have been caused by counterfeit battery packs.
This website provides information on various counterfeit products.

http://www.cipa.jp/battery/index_e.html

Same thing applies to cell phone batteries.

That's just crappy yet none too surprising. Another thing to avoid is Bluetooth headsets. eBay is running rampant with fake ones from all sort of manufacturers.