Pardon if I missed a previous thread, but my LBS is touting Shimano 10-speed drivetrains which I thought might only be beneficial for road bikes. The newer Shimano 10-speed chains seem obviously thinner (??and weaker)as one broke while trying it on my 9-speed cassette! and they promptly replaced it with a SRAM PC-99. So the question remains....why do we need 10-speed drivetrains on mtn-bikes; is it just market hype to combat competition or patent expiration; is it the "next logical step"; what about increased cassette wear and ghost shifting problems; and what gear ratios will be available(11-32, or 12-34, or others?). I guess soon we'll have a computer chip in the rear DR.