The holy grail of interactive media is to be more targeted. Behavioral targeting is when the online advertiser places the message in the path of the user, based on the user's past behavior. That's opposed to traditional targeting, where the online ad is placed against content the advertiser assumes the user will be interested in. It's one of those smart Internet ideas that's been surprisingly slow to catch on because it relies on sophisticated tracking technology. While the use of BT is growing, it is primarily only offered by a handful of companies.