There's a sea change in consumer advertising, and it's tangible. Traditional mass media advertising has been blindsiding consumers with the “commercial” for almost a century. They are gladly TIVOed out, and still remain at best tolerated, and at worst, an affront, a waste of time. The contextual commercial, an ad served based on the users' personal preferences, would seem to be a more attractive opt-in, but one only needs to be reminded of the deluge of “opt-in” emails to realize that streams of advertising in aggregate are still noise. I myself opt-in to nothing to avoid the deluge.
Simply put, the most effective advertisement now needs to provide immediate value to the consumer, and not be perceived as an overt, even oppressive play for brand equity. Commercials and banner ads, like spam and popup ads, will lose credibility because they are seen and suspected for what they are — a pushed brand sell without regard to the needs of its recipients. The value-laden ad needs to either 1) provide an immediate transaction solution to a problem, or 2) provide monetary benefit to the user.
1) Provide a transaction solution
The big problem with search engines is simply their inability to efficiently find the product or service one wants to buy at the best price, particularly on a local level. Try googling “tennis racquet sale in San Francisco“; you'll see that it's impossible to find a local sports store with a sale going on. Soon local retailers will post their weekly advertising circulars on Facebook, and the search engines, as well as Facebook's Open Graph initiative, will not only find these circulars in real time, but also track the conversations revolving the retailer and its current sales items across all social media (Yelp, Foursquare, Twitter, etc.). This is a practical and easy to understand example of what the contextual web will mean for consumers. Simply put, you can easily find what you need.
2) Provide monetary benefit
Extraordinary discounted deals and coupons that are truly valuable (and not the almost patronizing 10% off sale) will always be welcome. Broadcasting these deals is not perceived as advertising, they are “found money”. Groupon and its many imitators will reincarnate the Penny Saver coupon, but instead of arriving in the mail and being tossed, they will be followed and monitored by consumers who want to save 50%+ on a service or product they can use. Getting a bargain is an emotionally satisfying experience.