They treat developers like crap - Both those who use the platform and those who work at HQ. They fired me after 1 month during my probation because I was too slow to implement a feature because I was spending extra time writing tests. I remember the tech director telling me "That's not the kind of engineering we do here" after I tried to justify why tests were important. Several of these horrible people went on to work for Facebook later.
The CEO of Freelancer.com is a complete jerk. A few years after I had gone, I spoke with engineers who used to work there and there was gossip going round that the CEO had sex with a female employee and she got pregnant. He also hired his friends in top positions; some of which were utterly incompetent. Some of the CEO's favourite employees got drunk during work hours in front of the overworked engineers.
Employee retention was very low.