You. If you are on this site and hold any steem, you are, in a way, an owner of steemit. There are no stocks in the company, instead, there are steem coins. And everybody who holds steem coins wants to see them do well. This includes any user with any amount of steem, me, and the people who run the steemit company itself. If you check out the steemit account page you will see they have a LOT of the coin. This is a good thing, because it means they, just like you, have something to gain from the value going up. And if you are not a member of steemit and have found this on a Google search or a link from Twitter (feel free to post this link if you want to), then what are you waiting for, join for free and get some steem for yourself.
As everyone is holding steem, this leads to a community of people who want to see steemit succeed. This means people will actually care about what gets posted here and how popular the site it. This also means, if people think long term, they should care about the new users who enter the site and will be happy to see the numbers go up. They will also probably care about the content that is on here and they will want to see quality on the trending page. They will not want to see people scamming the system and will be happy with other users who work to support the network.
Steemit has also let the people decide what to do with the site. What becomes popular is up to whatever the people with SP decide to upvote. And when the hardfork 19 comes, the voting power should be spread out more. In case you don't know, that steem power that the steemit account has is not being used for voting. So it is up to the members of the site to utilize the site as they see fit. And it is up to you to post what you want to. You want to write, upload videos, photos or type a bunch of gibberish, go for it. If it gets likes or doesn't that is up to the users. It is an open system.
Welcome to a decentralized system where we are all here to both work alone and work together.
Go team steem.
*my upvotes/rep disclaimer: https://steemit.com/steemit/@whatageek/my-steemit-account-where-i-stand-on-bots-self-votes-and-multiple-account