Steemit dev blog announced ads will be coming on Steemit app https://steemit.com/steemit/@steemitblog/testing-ads-on-steemit-com
This was a long time coming event that should of been implemented long time ago to protect Steemitinc from brutal bear market. A little too late IMO because the traffic we used to have is mostly gone, the ads will generate way less than they could of generated before, due to bear market the traffic on Steemit is mostly gone. However, the ads will help at least a little to continue the development of Steem blockchain. This will not change anyone's experience while using Steemit, you can use adblock and it will be the same as before.
You can also use other Steem based social network blogging apps like busy, steeve, partiko, esteem, all those other apps don't use ads atm, but they all use Steem. That is the power of this blockhain, if you hate ads, just use some other application. Turns out Steem is pretty awesome.