Hello I am a 510 user that has relied on Strava primarily, and have also used the Fitbit Flex for roughly 2.5 years. The integration of segments, challenges, and badges in GC tell me that Garmin wants to increase social integration and not only act as a data hub for the individual. If this is the case, I highly suggest allowing the user to draw from their existing contacts on their computer/mobile device to see which of their existing friends are already GC members, making adding more seamless and intuitive. Integrating FB for this purpose would also be huge. Strava/Fitbit both enable this ability which allows new users to immediately add on friends and connections.
Having to seek out Connections one at a time, without knowing who has a GC account or not makes it difficult to "connect" with friends.