Despite recently canceling my dotMac account, I think this is important news because it highlights a use case of microformats which many have not recognized.
Up until now, most usage of hCard has been people publically publishing contact information. Putting it in hCard allows people to use X2V to convert it to a vCard, which most address book applications support.
In the case of dotMac’s webmail, the contact information isn’t public– it’s in a private view of an individual user. By marking up this data with hCard, browsers which understand hCard can recognize what they’re rendering and do smart things with it. Today, the best tool for doing this is the wonderful Tails Firefox extension. Tails will highlight microformats in a page and allow you to extact them to your address book or calendar.
My point in all of this? Semantic markup is valuable no matter where you use it– public or private– because it allows us to build smart tools for consuming the information.