For new users or people who do no understand how this site works, here is a clear explanation of why is not a Ponzi scheme. You do not have to invest a dime to use all the features of the network, you are not trying to bring in money from other users and the site works even if you take the money aspect out of it. Ponzi scheme applies it is a scheme to get money from people and has no real use. This is, without a doubt, a functioning social media/blog site with a unique system of voting power. You can take the money/market away from steem and have steem be points, where people with more points get more voting power and the site still works. And unless you have been under a rock for the last five years, social media and content distribution are BIG businesses that are not schemes. They are, arguably, one of the biggest businesses in the future. Plus the site give you rewards for free to use it, if it was a Ponzi scheme, this would be the dumbest scheme ever :p.
And even if you choose to buy the coin, you are buying it from an open market, which means you can be buying it from anyone who has it.
The future of media is all about the attention economy. Facebook, Netflix, Youtube, Steemit, your mother's blog are all competing for the same thing. Attention. And it will only get worse. People have more and more free time on their hands and access to media. It is a global market that people are fighting to get a piece off. Steemit has thrown their hat in a very competitive ring. The reward system and decentralized aspects give them a unique voice in a crowded market but they are up against tough opponents. But there are a company who are bringing in new ideas to filter content and reward the content creators. But they are, in no way, a Ponzi scheme.
*my upvotes/rep disclaimer: @whatageek/my-steemit-account-where-i-stand-on-bots-self-votes-and-multiple-account