The Windows Live Local/Virtual Earth team has a blog post entitled Free Phone calls at WLL which states
A new release of Live Local went out over the weekend. Mostly minor bug
fixes, but a few new features made it in as well. One of the more interesting is
the ability to phone any business for free. Using it is easy - do a business
search by name or category and in the result panel will be a 'Call for Free'
link next to each business listing. Each pushpin popup on the map will also have
the Call for free link. When you click it you specify your phone number -the
system will dial both you and the business and connect you. Once you've made
your first call, you can rapid dial businesses without having to re-enter your
Windows Live Local is definitely my favorite online mapping service today and probably the only Windows Live service I can say is head and shoulders above the competition. Kudos to everyone on the team who have built such a killer service in such a short time.