It's good to use the Bitshares as a 'company' metaphor to ease people's concerns. The structure of proof-of-stake is exactly how almost all companies work today.
I look at it from a corporate governance perspective. In a typical company shareholders elect the Board of Directors based on voting stake. The Board of Directors subsequently hire management. Sure this system is not perfect. There is potential for favoritism, shenanigans etc in hiring the Board as well as when the Board hires management, but these issues usually are not a major problem because companies must stay competitive and maintain or increase value. The incentive for the shareholders is to increase the companies value to increase everyone's stake, especially those that have the most on the line. I would expect wasting resources on a bad delegate for kick-backs would have a far greater chance of decreasing the total value of a large stakeholder's value compared to the value of any kick-backs they may receive. Imagine what even the perception of wrongdoing would do to stakeholder value. It's the same with companies. That being said it's always good to have controls in place just like most companies do and with greater transparency & controls the value of the company or DACs should increase. The DAC model creates more transparency and decentralization in corporate governance compared to typical private & public companies so shenanigans will be harder to sustain.