1. I think the news.ycombinator.com crowd is a really poor proxy for the 150M Americans on line.
2. People's ad blindness depends, at least in part, on the situation. Some sites hide context sensitive ads for registered/regular users, because they know that such users aren't likely to click on them. The users who are most likely to click on them are people who are actively searching for information, such as people who arrived by clicking on a search result. If they don't find the information they are looking for, they are going to move on. If the ad displayed is relevant, it presents an attractive place to move on to.
For my part, I usually completely ignore all the paid placements on the Google search results, but when I'm shopping for something, I'll click on the ads if people seem to have what I'm looking for.