Black Magic? Holding their families hostage?
Seriously though: I'm very interested in how they manage this company and the distributed employees as they are obviously doing a lot of things right.
'm sure working from home helps limit turnover too. Also, they work in teams, and I'm sure that's fun. And I've never noticed anyone mention things like logging time either - I think they get assigned work and as long as you get it done, time isn't an issue.
And finally the people that work for Automattic tend to be really really passionate about WordPress in the first place, so I'm sure working for the most influential company to the WordPress.org project(Automattic / wp.com), doing WordPress stuff all day, is pretty awesome.
Also, I get to work with really smart people that are driven to improve themselves, their co-workers, and the company's products. That's the #1 reason for the low turnover.