Flickr’s introduction of Friend Finder caused concern because even though they did it right it does allows for a bulk comparison of all your email contacts to the Flickr user database. “Security by obscurity” is important and expected by some.

Giving friends permission to access my location lets them share my location without my permission with apps I didn’t necessarily trust. This is a risk of data portability – others can port your data.

Under the hood the site combines a number of interesting technologies: OAuth, Fire Eagle, GeoNames and the new Google Static Maps API.