it would be great if most people put a little code on their paper business card.
you could give the card to someone you want to make contact with. if they saw the code they could, instead of typing in your contact information into their PIN (or using a card-scan reader), they could just type in the code and it would automatically download your most current information.
of course, ideally this would also work on a mobile phone.
i can't imagine why plaxo (or even linkedin, skype, or numerous sites that collect your information) couldn't do this today. if just a small portion of people adopted it, it would be a lifesaver for people that collect a lot of business cards (and very helpful to even the average person that collects a few). and it would be a great way of further advertising the service. i know i'd put it on my business card immediately...