"Move fast and break things" was one of the original Facebook company values. My sense was that the spirit of "move fast" was to work quickly, prototype or develop something scrappy and launch as soon as possible. The spirit of "break things" was to take risks and not think too much about every potential consequence knowing that if something failed, it would be okay. In reality, this happened all the time in the earlier days of Facebook where someone might push something and break the site temporarily. The underlying tone though was one of urgency to be on the cutting edge of what was possible for the user experience and stay ahead of competitors.

As the company got bigger and had more users, literally "breaking" the site was much more costly to the user experience and the company. At some point the company revised the value statement to simply "Move fast." but retained the spirit of taking risks and being bold.