IPhone – How to prevent sharing contacts between two iPhones without opening a new account

You don't mention if they're on the same computer. I am in a similar situation, two iPhones on one iTunes account, except we each sync to a different computer. I expect (based on the note above) to be able to upgrade both two iOS 5 and use two different iCloud accounts. As our data currently lives separately on two computers (Snow Leopard), I'm optimistic that we won't clobber one another. Perhaps this is an option for your friends?

Exporting your contacts from an iPhone is very easy: all data about the contact, from name, phone number, picture, email, URL, etc, can be exported as an inclusive vCard bundle from iCloud (or without for example with this app) and sent to someone else by email or text message. (While we’ll focus on sending contacts between iPhones, these vCards are also usable by other iOS devices, Macs, Windows, Windows Phone, Android, and even Blackberry phones, because the exported VCF format is pretty much universally accepted across all platforms as an address book standard.)

You’ll probably want to backup and sync the new iPhone beforehand just in case something goes haywire importing the vCard, however unlikely that is.

• log into te iCloud accound from your old iPhone and select all your contacts on the settings button (bottom left). It says Export vCard. Click this and you can Export all your contact information as a vCard .vcf file
• create an email with the vCard attachment and send it to yourself (or rather, the email on the other iPhone)
• On the other phone you can import the vCard: Open the email containing the contacts on the iPhone and tap on the vCard.vcf file attachment

• Tap on “Add All # Contacts” to import the address book to the iPhone

Notice the add option tells you how many contacts are stored within the vCard, making it easy to determine if all intended contact information is included. You can also manually select individual contacts from the list if you only wish to import one or two, but for the purpose here we’ll transfer them all over.