Contextual ads were the Next Big Thing in web advertising a few years back when Google launched the AdSense/AdWords program.  The idea that ad content could be directly related to content on the page was a new idea, and something people reacted very well to overall.  Ads were no longer just billboards trying to divert your attention, they were something that might actually add value to a site.  In general, efforts these past few years have focused on making web advertising more relevant, more interesting and generally less intrusive than in the past.  No one wants their product or service to be associated with an annoying user experience.

Well, it looks like we're getting ready to see a new shift in web advertising, and it's not Google who's in the lead this time, it's Yahoo.

Today, Yahoo launched a new ad product called SmartAds, which allows advertisers to target ads based on the individual user.  Age, gender, and browsing behavior across the Yahoo network of sites impacts the ads an individual will see.  Examples mentioned in a CNet article mention taking a user's previous search history into account when they're browsing another site.  Have you been researching high-end graphics cards recently through Yahoo Search?  On other Yahoo pages, you may start seeing more graphics card ads.

Behavioral targeting, combined with context-based advertising means we may start seeing very personalized ad content in the future.  But what are the implications?  There's already concern over companies like Google compiling profiles on users based on their search history, this is taking things a step further.  What happens when someone else uses your PC and they see ads based on your browsing?