Do you think if you were explicitly asked for what ads you would like to see that you would pay more attention to those ads?
Context ads are good, except when the ads aren't in the context of the site. Just because sex gets mentioned in an article, doesn't mean I want adverts for sex pheramones and when I read something on bargains on HDTVs I do want Bestbuy, FutureShop or eBay adverts popping up as I'm actively looking to buy something.