steemit service was founded in 2016 by Ned Scott and Dan Larimer, creator of BitShares.It is powered by an open source blockchain called Steem.
According to Investopedia, a blockchain is a public ledger of all [crypto-currency] transactions that have ever been executed...proof of all the transactions on the network.
The U.S. Securities and Exchange Commission (SEC) identifies seven red flags of a Ponzi scheme. If Steemit was such a scheme, it would be exposed here. Source of Ponzi red flags from the SEC:
https://www.sec.gov/answers/ponzi.htm
Becoming a user on Steemit does not require an initial investment. so its safe to say steemit is safe.
source @kennykelly