1: Blockchain, no chain no network
2: Witness', keeping the network strong and helping the community
3: Steemians, without them there is no steemit
But the hardest part of this question? Being the CEO of steemit would cause the platform to go from GREAT to EHHH. One man (or woman) should not have complete control (or most control) let the community shape the tide of Steemit.