Ad are certainly obnoxious. It is interesting to think that with a "reduced set" of features advertising would improve a website.

Advertising does more than detract from user experience. It is formative of consumer desire. Targeted ads in Vogue are appealing because I opt in to them. The information used to target me on the internet are behind my back. They support an incomplete feedback loop used by statistics to identify what market I belong in. I think this is what has a negative effect on user experience.