Good news on the Google blog:
Starting today, we’re adding CardDAV - an open protocol for contacts - to that list. CardDAV enables 3rd party clients, like the iOS contacts app, to sync your Google contacts. By supporting IMAP, CalDAV, and CardDAV together, we’re making it possible for 3rd parties to build a seamless Google Account sync experience.
Enabling CardDAV is very good news. This protocol doesn’t have the limitations Active Sync, the Microsoft Exchange protocol, has.
The iOS device can synchronize up to 3 email addresses. Phone number synchronization is limited to 2 Home numbers, 1 Home Fax, 1 Mobile, 1 Pager, 3 Work (one will be labeled ‘Company Main’) and one Work Fax number.
However, on the support page of CardDAV it says:
Syncing via CardDAV is only available over SSL for Apple devices on iOS version 5.0 and above. If you use Google Apps for Business, use Google Sync to sync your contacts.
Why is this? I just tested it on my iPhone and it works great. The only issue I can think of is support. Google cannot yet give their 99,995% guarantee because it is not yet thoroughly tested. And what better way to test it than on millions of Gmail users?
But then again, the first consideration on the Active Sync for Google Apps support page is:
Google Sync is still in beta. Read Known Issues with iOS before enabling Google Sync with iOS devices.
They might as well do the same for CardDAV. Thank you Google!