As long as the monarch is benevolent this is great, but then there's no mechanism to prevent abuses of power, and then maybe the monarch changes, or circumstances change, and the inevitable happens.
Google is making more money than ever, but that's still not enough for them. And now we're starting to see a lot of the "well, we chose not to be evil" slip away. The problem with "don't be evil" is that it's weak, and it's a double negative. Contrast it with "be good". Neutral isn't evil[1], and once you're down in the moral gray area pit anyway it's easy to move the goal posts and define "evil" differently. One could make a very well-founded argument, for example, that Microsoft, Oracle, Apple, and even EA or Comcast are not, strictly speaking, "evil" companies.
[1: what makes a man turn neutral?]