Open Alternatives

With all the frenzy about an open alternative to Twitter, Facebook, and whatever will come after those, I want to understand why open alternatives are better. It's just assumed, isn't it?

First: what are some successful open alternatives?

• • Mozilla as an alternative to Internet Explorer

  • LAMP stack (for the back-end of the WWW)

  • The Internet as an alternative to however we lived before

That's it?

Is an open alternative to Facebook going to work? If it's distributed, some people say forget it. Does calling it an open alternative condemn it to failure?