Scobleizer may have scoped it (and provided the following interview with the chief platform architect and VP of marketing):

As usual, it’s TechCrunch that has the most user-friendly article:

Plaxo 3.0, a new version that builds on its multi-point sync product by offering improved sync options as well as a feed-style people tracker. Automated “multi-way sync” under Plaxo 3.0 includes Google Calender, Microsoft (Outlook, Outlook Express, Vista Mail, and Hotmail), Yahoo (Mail and Calendar), Mac OSX (for Address Book, iCal, and iPhone), AOL (AIM and Classic AOL), Mozilla Thunderbird and LinkedIn. The new multi-component “smart address book” web app includes tabs for contacts, calendar, tasks, notes, and more.