You can create a new user interface to Steem (because it's open source blockchain). Steemit.com is just the first one and I bet there will be many others – whether or not Steemit has ads in the future. All messages are in the blockchain so it's up to users how they want to use it.
I'd rephrase this a little bit:
You can create a new user interface to Steem (because it's open source blockchain). Steemit.com is just the first one and I bet there will be many others – whether or not Steemit has ads in the future. All messages are in the blockchain so it's up to users how they want to use it.
Edited thank you