Hints at a .Mac online Address Book appeared in November... and it appears that this feature will be available starting at MacWorld San Francisco. Apple's .Mac page describes the following feature:
- .Mac Address Book with contact synchronization
Enjoy access to your key contact information anywhere. Your online .Mac Address Book will soon work with iSync so you can have all your key contact information, including addresses and phone numbers up to date. A great feature when you're on the road.
An image promoting this feature is stamped "Available Jan. 7".