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 world, however, doing that results in the message "Download failed. Safari cannot download this file" being displayed. So, my question is, is it actually possible to add a contact to your iPhone's Address Book from a web page?
I have both the original VCF file and an hCard microformatted version of the data available to me, so the solution does not have to be tied to downloading the original file - I'm able to reprocess the data if necessary. The only requirement is to add the contact to the iPhone's Address Book from a webpage being viewed from within Mobile Safari.
So, any ideas?
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