Think about it , add companys would love to get there peice of the pie with steem users growing every day, if they had to buy steem to place the adds on steem, the price would grow drastically as demand would be less , adds for the user could be optional, and if accepted a small amount of steem payed..Something like the Basic Attention Token (BAT) could also be implemented so adds are more targeted and engaging the viewer, not just spamy kind of adds... Just a thought, let me kno what your thoughts are on the possible implementation of optional adds, and if it would be beneficial or detrimental to the steem community ..