Microsoft has responded to user concerns about the type of information that's transmitted and used when you use the new Windows Live Local "locate me" feature. From a blog post by Chandu Thota, SDE Lead of the Microsoft Virtual Earth team:
No personal information such as your name or contact information is sent to Microsoft by Location Finder service. Also, Location Finder service was designed with concern for your personal information; secure methods such as SSL are used when transferring location information between your machine and the Microsoft location service.
The post also notes that no information is shared, and offers a bit more technical detail about how the feature works. Reassuring information if you're concerned when you use this cool new feature from Microsoft.