The industry term is "behavioral ad targeting." What it means is, advertisers are tracking young social networkers' (and everyone else's) online behavior the better to persuade them to "sell" the companies' products to their friends. "Internet start-ups out to crack the problem of advertising on social networks are developing ad technology that can analyze which people are most influential to their friends on social networks so that they can target those people with pass-it-on messages about Apple's latest iPhone or The Incredible Hulk movie," CNET reports. Widgets, those little applications that social networkers install in their profiles, are the key. Startups such as SocialMedia Networks and 33Across use them to figure out, with a mathematical algorithm, which friends are most important to the person with the profile – to decide which friends should be in a banner ad on the profile. Interesting: using math to qualify friendship. Anyway, here's CNET reporter Stefanie Olsen's example: "Instead of a banner advertising The Incredible Hulk movie, a social banner would ask which of your close Facebook friends, among a short list, you'd like to invite to see the movie. Or a social banner might inform you that a friend Jim just ranked Iron Man with three stars, and it might ask to 'click here to buy tickets at Fandango'."