As I posted in a response to another user, advertisement does not need to all be put on the back of steem. Almost all other front ends to the steem blockchain advertise:

posted with partico
posted with esteem
posted with Busy
Posted with steeve

These are all micro ads.

A lot of the bloggers advertise with all the footer's on their pages. For a proof of concept thing and to test the viability of ads, talk one of the other front end providers into an advertisement test.

Have one of the above auto include a steemmonsters banner linked to the steemmonsters web page appended to the bottom of all the post made through their front end. The ad could even be formulated to scale down to be added on a comment.

This would show people either the acceptability or not of an ad being placed that they have no control over, on their post their comment.

The other thing to remember about advertisers, is they like being able to control the narrative, look at how many times in the past advertisers have pulled their advertising from various media outlets in the past several years.

Are the people that run family friendly sites going to be receptive to a Trojan Condom advertisement on their post? What kind of advertisements would then be the fault of steem? Would an atheist site welcome the New Age Bible sales advertisement on their page, the vegans having to see Wendys hamburgers advertised on their pages?

It is a big kettle of fish when advertisements and advertising is brought up. But like I said I do not think it would be that hard to add an advertising footer banner to any post at all.

There just needs to be a lot thought about than just blanketly talking about adding advertisements. Who, what, where, why, when it comes to advertising, Who is allowed to advertise? What are they allowed to advertise? Why are they allowed to advertise and the other guy is not? People need to think serious about advertisement and advertising, it could have some very negative consequences.