In the desktop Mac world, if I were to click on a link in a web page which linked to a VCF file, this file would be opened in the Address Book application. In the iPhone wo
Whilst slightly outside of the scope of my original requirements, I have found a solution to the problem that I can work with.
As it turns out, if you receive an email with a vcard in it as an attachment, then you are able to open this attachment and add it to your address book. So, if instead of offering a vcard download link to iPhone users you provide them with a way to be sent the vcard via email instead then they are able to add the card to their address book.
A slightly roundabout solution, but about the best I'm able to come up with whilst Apple don't allow you to do it natively. Certainly it's a better solution than doing nothing at all.
I ended up writing a blog post about this: Adding a vCard to your iPhone Address Book from a web page