Ads or no ad? Can it be so arbitrary?

Ads or no ad? Can it be so arbitrary?

All right, I'm kind of confused here. HMF explained the reason why the retail price will be lower and quantity will be higher with advertisement. However, the success of craigslist is base on no-ads. Then I'm kind of confused now.

So does advertisement attract more eyeballs or push eyeballs away? I was trying to discuss with my roommate, who majors in advertisement. She said if the amount of content remains the same then advertisement won't really hinder readers. So I think the key is the ratio of content and ads, and I'll probably assume users prefer higher content. (I was trying to develop a math variable to HMF's graph, and then I found it's going to be too complicated.)

Wait, I buy Sunday newspaper simply because the coupon. Isn't that an example of ads raise the quantity? (Even though the causal relationship is different from the one in HMF.) I'll rush to a website if there are coupons that I need, too. But that's coupon rather than pure ads. So should we discuss coupon and ads together or separately?

And readers seem to hold different tolerance of printed ads and online ads. The ads on a newspaper seem to be less annoying than website banner ads, at least that's how I feel. But why?

Still have no idea about the relationship between advertisement and news media.