The "break fast and move things" mantra isn't black and white, nor is it universal. It is a general alignment that, at the high level says, don't be afraid to make calculated mistakes but be prepared to quickly respond to feedback and those mistakes as appropriate.

That means a privacy or a security issue will be tackled with the utmost urgency--we would even shut down the site if we didn't have a quick fix for a security/privacy bug. However, if one of the Timeline aggregations isn't working or if a particular text box is not aligned, then we will fix it with the next release (usually in another day or half).

So it's not true that "move fast and break things" means "it's OK to introduce privacy/security holes" or even "it's OK to release shitty products". It just means we push early and push often.