Diaspora
No discussion of open social networking would be complete without a look at Diaspora. This project was announced to great fanfare last year. Shortly after the announcement, it became clear that it was a dead end.
Rather than focus on the important foundationsa solid protocol for interoperabilitythe developers started working on the user interface first. While the UI is important for a finished product, this approach is rather reminiscent of those old Windows applications with a set of windows designed in Visual Basic and no code behind them.
This could perhaps have been forgiven if the implementation had been good, but unfortunately it was a disaster, full of security holes and poor UI choices. Not only did they decide not to use one of the existing standards, the one that they invented was poorly thought out, subject to no public review before their first public implementation, and full of security holes.
Diaspora has been quiet for most of the last year, so hopefully we've heard the last of the project.