The World of Contact Synchronization In The Cloud

What would you guess is probably the #1 feature that almost every single user wants of every single on-line address book service?

If you guessed bi-directional synchronization, you'd be right.  Unfortunately, it is not as easy as people think.

For the purposes of this discussion, we are going to remove portable devices (Blackberry, iPhone, Android, Exchange, and Windows Phone).

Breaking contact synchronization to its simplest components- there are 3 main webmail services where most people keep their address books:

Then there are 2 main social networks that everyone seems to use:

Unfortunately, since none of these services automatically talk to each other, third-party services have started popping up to act as the middle-man:

BUT, then the world gets A LOT MORE COMPLICATED