An alternative solution is to never store contact details locally; only URLs, and to fetch the contact details each time you need to use them – but of course that requires an “always on” connection and has several potential single-points-of-failure.

No objection to throwing a URL in the mix as well… but the key to this idea is not a vCard or microformat piece of text – because in order for that to remain relevant, the user would have to revisit the site, redownload the updated information, and re-import it into their system.

The trick here is more along the lines of the kind of dynamic updates that Plaxo do (the one bit they do well, though their service is a mess of far too many ideas) – and with the integration into social and business networking sites through API.

In other words – the whole point is that you put the information into your computer only once (and without effort) and then a) it’s always up to date, no matter what happens; and b) you can connect to that person through whatever platforms they enable and you select.