I've long considered handshaking a barbaric Germanic relic which ought to have been done away with alongside trial by ordeal, and once you read this BBC article you'll see why I feel the way I do. From reading research surveys and watching how others behave in public facilities, I've come to understand that most people either have no idea what proper handwashing technique entails*, or else they're simply too lazy and slovenly to act on this knowledge; as such, whenever possible I'd rather just give a friendly wave and say "Hi" rather than grab anyone else's grubby mitts. As far as I'm concerned the Japanese have the right idea - a simple bow ought to suffice to acknowledge someone else without having to share the person's faecal, respiratory and skin pathogens - and that is precisely what the disgusting habit of handshaking entails. To think that the vast majority of people compound such filthy habits with a reluctance to wash their hands before eating turns my stomach.
*Hint: If you take less than 10 seconds to "wash" [sic] your hands, you're not doing much more than engaging in meaningless ritualistic activity, as it is the mechanical action of actually using soap to scrub the germs away which counts, and that takes time to do properly: soap does not actually kill many bacteria and viruses, and what it does is simply detach the germs from one's skin so that the water can wash them away. I'm always pleasantly surprised when I see someone wash his or her hands properly, and I say "surprised" because it happens so rarely!