Mmh, @asher though topic.
First of all I don't have any problems with a small doze of advertising. Small is here the keyword. Let's take Scorum as example! They do have adds placed on their pages. And they are placed smart. They do catch attention but they don't distract!
Secondly: I don't think the adds should enrichen the users of the steem blockchain only. It should also support the witnesses and the ones who do have to pay for the infrastructure. Otherwise, the user could get more steem and the problems for the ones who do pay the infrastructure do stay the same.
Also here we could use Scorum again as example. Where 40% of the income of the adds will go to the reward pool and the others will go the ones who do have to pay the infrastructure and the witnesses!

So adds fine by my but the rewards should be distributed fairly and depending on the costs they have. Maybe for the users the showing/viewing for adds is the price they have to pay to make use of this free blockchain!

And we do have to face the fact that adds are already present on steem. Most of all the post on Trending are paid advertising, only here the money flows to the entrepreneurs who did develop the upvote bots.

Also if they are going to allow adds, is this then only on the steemit frontend or will they force this also on @busy, @esteem or @steevie ?
@steevie understood that nothing is really for free and took some measures. Like a part of the curation if they proposed the post, the offer the possibility to put steevie as beneficiary reward.
Maybe this last is a better solution.
Suppose that steem.inc would get 1 or 2% beneficiary of each post! You have a better insight in how much is extracted from the reward pool. By doing this they would get paid for each transaction on the steem blockchain, which they can use to pay for a part of the costs.
Don't know how many people would agree with a measure like this but I am just trying to think outside the box!

Cheers,
Peter