If users saw and clicked on ads, but never bought anything, then it would be the merchants who paid the advertiser suffering, instead of the content provider. The merchant would have to start looking for other ways to promote awareness of, and desire for, their product. The advertiser would start to become obsolete, and the "ad supported content" business model would deteriorate. I propose that this business model is doomed to the tragedy of the commons, and that society must evolve past it or protect it with force. There are alternatives, some more likely than others to succeed.
I would love to have more live interaction with the content providers, and would certainly be willing to pay for it with money, time, and labour. Debates, concerts, group art / cooking / hacking sessions, instruction and training in small classes, participatory filmmaking à la Jackass, interaction with architects before building my own home, the list is endless. Many of these activities could produce trivially replicated works of art, and I would give them away for free just to be cool and to make my society more vibrant, fun and useful for all of us.
This raises a concern for the welfare of the advertisers themselves, who the users are basically cutting out of the loop. I have a friend in advertising, living hand to mouth, so this is a personal concern for me as an individual, because the welfare of my peers affects the power of my social network to help me as an individual member; the same reasoning applies to a lesser extent to my society as a whole. Perhaps the advertisers need to see themselves as artists, and focus on working within this same framework to produce desirable art that promotes (or disparages) the products they would have advertised (or helped us ignore). Comedy, debates, and live reviews with Q&A sessions are all things that I could see a talented advertiser doing.
I am starting to see a pattern here: There is too much "one to world" interaction in our society, and not enough one to one or "one to group". Altering this imbalance will cost the consumer more than just downloading or 3D printing everything for free, but this could be OK as more live art in a capitalist society should prevent it's cost from becoming unreasonable. Canucks tickets, anyone?