I join a lot of social networks. It's part of what I do to keep ahead of where the audiences are going. The latest rage is direct messages. You can use the social network system to send messages to others in the network. Twitter, Facebook, Flickr and many others have this tool.
The problem with this feature, however, is that it's basically like having another email account. When people send you messages through the system, you need to log in and use it to read the notes and respond. It's great that these networks are flat hierarchies. However, direct messaging systems add to The Attention Crash.
As social networks begin to really tap into their analytics and search data, they will become virtual brains that know what you're interested in and what you're circle of friends are following. Then these systems will be able to push content and advertising that's highly relevant to you. Further, you will be able to personalize your results. You also will be able to control this setting based on your privacy preferences.
That's how these direct messaging systems should be used - as a funnel for content to find you. Flickr Explore does this to some degree, but the interface should be some sort of syndicated system like email or RSS. All other communications should go to your regular email where you can respond via a pass-through that funnels your note back through the social network to protect everyone's email addresses.
