Not to beat this thing forever, but here is a statement from Canon:
Safety Notice: Counterfeit Lithium-Ion Battery Packs (Update)
Updated: December 11, 2006
Affected products:
All Digital SLR Cameras, All PowerShot Cameras, All Digital Video Cameras
The purpose of this document is to notify you that counterfeit lithium-ion battery packs and battery chargers are being used with Canon brand Digital Cameras and Digital Camcorders. Canon recently discovered these counterfeit lithium-ion battery packs and chargers on sale, and in circulation on internet auction websites, being passed off as Canon genuine lithium-ion battery packs and chargers. Canon also learned of an explosion which appears to have been caused by one of these counterfeit lithium-ion battery packs.
Because these counterfeit lithium-ion battery packs and battery chargers are often not equipped with certain protective devices meeting Canon's and the industry's basic quality standards, using or recharging these counterfeit lithium-ion battery packs could cause your camcorder to malfunction, or lead these battery packs to overheat, leak liquids, ignite, or explode. In the worst case, this could not only damage your camera or camcorder, but also result in fire, burns and/or injuries (including loss of eyesight). Accordingly, these counterfeit lithium-ion battery packs and/or battery chargers should not be used.
Please be advised that Canon is not responsible, and will not be liable, for any malfunctions, damages or injuries caused by non-Canon genuine lithium-ion battery packs and/or battery chargers (including any counterfeit products).
For questions about "Counterfeit" products, please contact us at the following:
Telephone: 1 (800) 828-4040.
I find the next to last paragraph particularly interesting. Of course Canon is just following good CYA policies but it is worth noting.